diff --git a/.gitmodules b/.gitmodules
deleted file mode 100644
index c60caa6343..0000000000
--- a/.gitmodules
+++ /dev/null
@@ -1,4 +0,0 @@
-[submodule "exts/dbcsr"]
-	path = exts/dbcsr
-	url = https://github.com/cp2k/dbcsr
-	branch = master
diff --git a/exts/Makefile.inc b/exts/Makefile.inc
deleted file mode 100644
index 50e19cce30..0000000000
--- a/exts/Makefile.inc
+++ /dev/null
@@ -1,63 +0,0 @@
-ifeq ("","$(wildcard $(EXTSHOME)/dbcsr/src)")
-$(error "No DBCSR submodule available, please run 'git submodule update --init --recursive'")
-endif
-
-LIBS     := -L$(LIBEXTSDIR)/dbcsr -ldbcsr $(LIBS)
-EXTSDEPS_LIB = $(LIBEXTSDIR)/dbcsr/libdbcsr$(ARCHIVE_EXT)
-EXTSDEPS_MOD = $(OBJEXTSDIR)/dbcsr/dbcsr_api.mod $(OBJEXTSDIR)/dbcsr/dbcsr_tensor_api.mod
-$(EXTSDEPS_MOD) : ; # override builtin .mod rule to prevent circular dependency
-
-# Set Acceleration flags if glue code is supposed to be accelerated
-ifneq (,$(findstring __DBCSR_ACC,$(OFFLOAD_FLAGS) $(FCFLAGS)))
-# By default, we use CUDA if OFFLOAD_TARGET is not specified
-ifeq (,$(OFFLOAD_TARGET))
-DBCSR_USE_ACCEL = cuda
-else
-DBCSR_USE_ACCEL = $(OFFLOAD_TARGET)
-endif
-ifeq (cuda,$(DBCSR_USE_ACCEL))
-DBCSR_ACC      := $(OFFLOAD_CC)
-DBCSR_ACCFLAGS := $(OFFLOAD_FLAGS) -Xcompiler='-Wno-error'
-else ifeq (hip,$(DBCSR_USE_ACCEL))
-DBCSR_ACC      := $(CXX)
-DBCSR_ACCFLAGS := $(CXXFLAGS) -Wno-error=unused-parameter
-else ifeq (opencl,$(DBCSR_USE_ACCEL))
-DBCSR_ACC      := $(CC)
-DBCSR_ACCFLAGS := $(CFLAGS)
-else
-$(error "Invalid OFFLOAD_TARGET=$(OFFLOAD_TARGET)")
-endif
-endif
-
-extversions: dbcsrversion
-
-extclean: dbcsrclean
-	@echo "Clean EXT"
-
-dbcsr:
-	+$(MAKE) -C $(EXTSHOME)/$@ -f $(EXTSHOME)/build_$@/Makefile \
-	   ARCHFILE=$(ARCHDIR)/$(ARCH).$(ONEVERSION) \
-	   LIBDIR=$(LIBEXTSDIR)/$@ \
-	   OBJDIR=$(OBJEXTSDIR)/$@ \
-	   USE_ACCEL="$(DBCSR_USE_ACCEL)" \
-	   ACC="$(DBCSR_ACC)" \
-	   ACCFLAGS="$(strip $(DBCSR_ACCFLAGS))"
-
-dbcsrversion:
-	@$(MAKE) -C $(EXTSHOME)/dbcsr -f $(EXTSHOME)/build_dbcsr/Makefile \
-	   ARCHFILE=$(ARCHDIR)/$(ARCH).$(ONEVERSION) \
-	   USE_ACCEL="$(DBCSR_USE_ACCEL)" \
-	   ACC="$(DBCSR_ACC)" \
-	   ACCFLAGS="$(strip $(DBCSR_ACCFLAGS))" \
-	   version
-
-dbcsrclean:
-	@echo "Clean DBCSR"
-	@$(MAKE) -C $(EXTSHOME)/dbcsr -f $(EXTSHOME)/build_dbcsr/Makefile \
-	   ARCHFILE=$(ARCHDIR)/$(ARCH).$(ONEVERSION) \
-	   LIBDIR=$(LIBEXTSDIR)/$@ \
-	   OBJDIR=$(OBJEXTSDIR)/$@ \
-	   USE_ACCEL="$(DBCSR_USE_ACCEL)" \
-	   ACC="$(DBCSR_ACC)" \
-	   ACCFLAGS="$(strip $(DBCSR_ACCFLAGS))" \
-	   clean
diff --git a/exts/README.md b/exts/README.md
deleted file mode 100644
index 10d92754eb..0000000000
--- a/exts/README.md
+++ /dev/null
@@ -1,5 +0,0 @@
-# This directory provides access to external libraries via GIT submodules
-
-Please refer to the external repositories for any changes:
-
-* [DBCSR](https://github.com/cp2k/dbcsr)
diff --git a/exts/build_dbcsr/Makefile b/exts/build_dbcsr/Makefile
deleted file mode 100644
index 0702f450d2..0000000000
--- a/exts/build_dbcsr/Makefile
+++ /dev/null
@@ -1,335 +0,0 @@
-# This Makefile is only used for the inclusion of the DBCSR library into CP2K.
-# It is not supported by DBCSR development anymore.
-############################################################
-#### DO NOT CHANGE AS PART OF THE DBCSR DEVELOPMENT!!!! ####
-############################################################
-# CP2K team will update it, following the compilation flags suggested in the
-# CP2K installation file.
-# For this reason, this Makefile must be compatible with the CP2K
-# compilation and tested within CP2K.
-#
-# The ARCH file can set the variables:
-#
-# CC  => C compiler, e.g. gcc or mpicc
-# FC  => Fortran compiler, e.g. gfortran or mpifort
-# LD  => Linker, e.g. gfortran or mpifort
-# AR  => Archive command, e.g. ar -r
-# CXXFLAGS  => C++ compilation flags
-# CFLAGS    => C compilation flags
-# FCFLAGS   => Fortran compilation flags
-# LDFLAGS   => Linker flags
-# LIBS      => Libraries
-# ACC       => ACC can be nvcc (CUDA), mpicxx/mpicc or gcc/g++ (HIP), or mpicc/gcc (OpenCL)
-# ACCFLAGS  => ACC flags
-# USE_ACCEL => hip, cuda, or opencl
-# GPUVER    =>
-#          - for CUDA, possible values correspond to NVIDIA GPUs:
-#            possible values are K20X, K40, K80, P100, V100
-#          - for HIP, possible values correspond to NVIDIA and AMD GPUs:
-#            possible values are K20X, K40, K80, P100, V100, Mi50, Mi100, Mi250
-#          - for OpenCL, GPUVER maps to a file with tuned parameters:
-#            src/acc/opencl/smm/params/tune_multiply_GPUVER.csv, or
-#            src/acc/opencl/smm/tune_multiply.csv (default)
-#
-# Libraries for accelerator:
-#    - e.g. for CUDA:   LIBS += -lstdc++ -lcudart -lnvrtc -lcuda -lcublas
-#    - e.g. for HIP:    LIBS += -lstdc++ -lhiprtc -lhipblas
-#    - e.g. for OpenCL: LIBS += -lOpenCL
-
-#
-SHELL = /bin/sh
-#
-# the home dir is taken from the current directory
-#
-DBCSRHOME    := $(CURDIR)
-DBCSRCP2K    := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
-MAKEFILE     := $(DBCSRCP2K)/Makefile
-LIBDIR       := $(DBCSRHOME)/lib
-OBJDIR       := $(DBCSRHOME)/obj
-TOOLSDIR     := $(DBCSRHOME)/tools
-FYPPEXE      := $(TOOLSDIR)/build_utils/fypp/bin/fypp
-SRCDIR       := $(DBCSRHOME)/src
-TESTSDIR     := $(DBCSRHOME)/tests
-ARCHFILE     :=
-CXXSTD       := -std=c++14
-
-PYTHON       := /usr/bin/env python3
-
-# Default Target ============================================================
-LIBNAME      := dbcsr
-LIBRARY      := lib$(LIBNAME)
-default_target: $(LIBRARY)
-
-# Read the version ==========================================================
-include $(DBCSRHOME)/VERSION
-ifeq ($(DATE),)
-  DATE = "Development Version"
-endif
-
-# Read the configuration ====================================================
-ifeq (,$(ARCHFILE))
-$(error ARCH file must be provided: ARCHFILE=<CP2K ARCH file>)
-endif
-ifeq (, $(wildcard $(ARCHFILE)))
-  $(error ARCH file `$(ARCHFILE)` not found)
-endif
-include $(ARCHFILE)
-
-# Set the ARCH version ======================================================
-ifeq ($(GPUVER),K20X)
-  ARCH_NUMBER = 35
-else ifeq ($(GPUVER),K40)
-  ARCH_NUMBER = 35
-else ifeq ($(GPUVER),K80)
-  ARCH_NUMBER = 37
-else ifeq ($(GPUVER),P100)
-  ARCH_NUMBER = 60
-else ifeq ($(GPUVER),V100)
-  ARCH_NUMBER = 70
-else ifeq ($(GPUVER),A100)
-  ARCH_NUMBER = 80
-else ifeq ($(GPUVER),A40)
-  ARCH_NUMBER = 86
-  override GPUVER := A100
-else ifeq ($(GPUVER),H100)
-  ARCH_NUMBER = 90
-else ifeq ($(GPUVER),Mi50)
-  ARCH_NUMBER = gfx906
-else ifeq ($(GPUVER),Mi100)
-  ARCH_NUMBER = gfx908
-else ifeq ($(GPUVER),Mi250)
-  ARCH_NUMBER = gfx90a
-else ifeq (,$(ARCH_NUMBER))
-ifneq ($(ACC),)
-ifneq (opencl,$(USE_ACCEL))
-  $(error Unknown ARCH_NUMBER since GPUVER="$(GPUVER)" is not recognized)
-endif
-endif
-endif
-
-# Set ACCFLAGS ==============================================================
-
-# Adjust C++ standard level
-override ACCFLAGS := $(CXXSTD) $(filter-out -std=c++11,$(ACCFLAGS))
-
-# If compiling with nvcc
-ifeq (cuda,$(USE_ACCEL))
-  override ACCFLAGS := -D__CUDA -DARCH_NUMBER=$(ARCH_NUMBER) $(filter-out -D__CUDA,$(ACCFLAGS))
-  CXXFLAGS := -D__CUDA $(filter-out -D__CUDA,$(CXXFLAGS))
-  FCFLAGS := -D__CUDA $(filter-out -D__CUDA,$(FCFLAGS))
-  #if "-arch" has not yet been set in ACCFLAGS
-  ifeq (,$(findstring -arch,$(ACCFLAGS)))
-    override ACCFLAGS := -arch sm_$(ARCH_NUMBER) $(ACCFLAGS)
-  endif
-  ifeq (,$(findstring -Xcompiler,$(ACCFLAGS)))
-    override ACCFLAGS := $(ACCFLAGS) -Xcompiler="$(CXXFLAGS)"
-  endif
-# If compiling with hipcc
-else ifeq (hip,$(USE_ACCEL))
-  override ACCFLAGS := -D__HIP -DARCH_NUMBER=$(ARCH_NUMBER) $(filter-out -D__HIP,$(ACCFLAGS))
-  CXXFLAGS := -D__HIP $(filter-out -D__HIP,$(CXXFLAGS))
-  FCFLAGS := -D__HIP $(filter-out -D__HIP,$(FCFLAGS))
-# OpenCL backend
-else ifeq (opencl,$(USE_ACCEL))
-  CFLAGS := -D__OPENCL $(filter-out -D__OPENCL $(CXXSTD),$(if $(ACCFLAGS),$(ACCFLAGS),$(CFLAGS)))
-endif
-
-# Set the configuration =====================================================
-ifneq ($(LD_SHARED),)
-  ARCHIVE_EXT := .so
-else
-  ARCHIVE_EXT := .a
-endif
-
-# Declare PHONY targets =====================================================
-.PHONY : dirs makedep \
-         default_target $(LIBRARY) \
-         clean version
-
-# Discover files and directories ============================================
-ALL_SRC_DIRS       := $(shell find $(SRCDIR) -type d | awk '{printf("%s:",$$1)}')
-LIBSMM_ACC_DIR     := $(shell cd $(SRCDIR) ; find . -type d -name "libsmm_acc")
-LIBSMM_ACC_ABS_DIR := $(shell find $(SRCDIR) -type d -name "libsmm_acc")
-
-ALL_PKG_FILES := $(shell find $(SRCDIR) -name "PACKAGE")
-OBJ_SRC_FILES  = $(shell cd $(SRCDIR); find . ! -name "dbcsr_api_c.F" ! -name "dbcsr_tensor_api_c.F" -name "*.F")
-OBJ_SRC_FILES += $(shell cd $(SRCDIR); find . -type f -name "*.c")
-
-# if compiling with GPU acceleration
-ifneq ($(ACC),)
-ifeq (cuda,$(USE_ACCEL))
-  # All *.cpp files belong to the accelerator backend common between CUDA/HIP
-  OBJ_SRC_FILES += $(shell cd $(SRCDIR); find . -type f ! -name "acc_cuda.cpp" ! -name "acc_hip.cpp" -name "*.cpp")
-  OBJ_SRC_FILES += $(LIBSMM_ACC_DIR)/../cuda/acc_cuda.cpp
-  # Exclude autotuning files
-  OBJ_SRC_FILES += $(shell cd $(SRCDIR); find . -type f ! -name "tune_*_exe*_part*.cu" ! -name "tune_*_exe*_main*.cu"  -name "*.cu")
-else ifeq (hip,$(USE_ACCEL))
-  # All *.cpp files belong to the accelerator backend common between CUDA/HIP
-  OBJ_SRC_FILES += $(shell cd $(SRCDIR); find . -type f ! -name "acc_cuda.cpp" ! -name "acc_hip.cpp" -name "*.cpp")
-  OBJ_SRC_FILES += $(LIBSMM_ACC_DIR)/../hip/acc_hip.cpp
-# OpenCL backend: OBJ_SRC_FILES already includes all *.c files
-endif
-endif
-
-# Include also source files which won't compile into an object file
-ALL_SRC_FILES  = $(strip $(subst $(NULL) .,$(NULL) $(SRCDIR),$(NULL) $(OBJ_SRC_FILES)))
-ALL_SRC_FILES += $(shell find $(SRCDIR) -name "*.f90")
-ALL_SRC_FILES += $(shell find $(SRCDIR) -name "*.h")
-ALL_SRC_FILES += $(shell find $(SRCDIR) -name "*.hpp")
-
-# stage 1: create dirs and run makedep.py.
-#          Afterwards, call make recursively again with -C $(OBJDIR) and INCLUDE_DEPS=true
-ifeq ($(INCLUDE_DEPS),)
-$(LIBRARY): dirs makedep
-	@+$(MAKE) --no-print-directory -C $(OBJDIR) -f $(MAKEFILE) $(LIBDIR)/$(LIBRARY)$(ARCHIVE_EXT) INCLUDE_DEPS=true DBCSRHOME=$(DBCSRHOME)
-dirs:
-	@mkdir -p $(OBJDIR)
-	@mkdir -p $(LIBDIR)
-version:
-	@echo "DBCSR Version: "$(MAJOR)"."$(MINOR)"."$(PATCH)" ("$(DATE)")"
-else
-# stage 2: Include $(OBJDIR)/all.dep, expand target all, and get list of dependencies.
-
-# Check if FYPP is available  ===============================================
-ifeq (, $(shell which $(FYPPEXE) 2>/dev/null ))
-  $(error No FYPP submodule available, please read README.md on how to properly download DBCSR)
-endif
-
-endif
-
-clean:
-	rm -f $(LIBSMM_ACC_ABS_DIR)/parameters.h $(LIBSMM_ACC_ABS_DIR)/smm_acc_kernels.h $(LIBSMM_ACC_ABS_DIR)/*.so
-	rm -f $(LIBSMM_ACC_ABS_DIR)/../opencl/smm/opencl_kernels.h
-	rm -f $(TESTSDIR)/libsmm_acc_unittest_multiply.cpp
-	rm -f $(TESTSDIR)/libsmm_acc_timer_multiply.cpp
-	rm -rf $(OBJDIR)
-
-# Libsmm_acc stuff ==========================================================
-ifneq ($(ACC),)
-ifneq (opencl,$(USE_ACCEL))
-ACC_KERNEL := $(wildcard $(LIBSMM_ACC_ABS_DIR)/kernels/*.h)
-ACC_PARAMS := $(wildcard $(LIBSMM_ACC_ABS_DIR)/parameters/parameters_$(GPUVER).json)
-$(LIBSMM_ACC_ABS_DIR)/parameters.h: $(LIBSMM_ACC_ABS_DIR)/generate_parameters.py $(ACC_PARAMS)
-	cd $(LIBSMM_ACC_ABS_DIR); $(PYTHON) generate_parameters.py --gpu_version=$(GPUVER)
-$(LIBSMM_ACC_ABS_DIR)/smm_acc_kernels.h: $(LIBSMM_ACC_ABS_DIR)/generate_kernels.py $(ACC_KERNEL)
-	cd $(LIBSMM_ACC_ABS_DIR); $(PYTHON) generate_kernels.py
-endif
-endif
-
-# automatic dependency generation ===========================================
-MODDEPS     = "lower"
-MAKEDEPMODE = "normal"
-ifeq ($(HACKDEP),yes)
-MAKEDEPMODE = "hackdep"
-endif
-
-# this happens at stage 1
-makedep: $(ALL_SRC_FILES) $(ALL_PKG_FILES) dirs
-ifeq ($(LD_SHARED),)
-	@echo "Removing stale archives ... "
-	@$(PYTHON) $(DBCSRCP2K)/check_archives.py $(firstword $(AR)) $(SRCDIR) $(LIBDIR)
-endif
-	@echo "Resolving dependencies ... "
-	@$(PYTHON) $(DBCSRCP2K)/makedep.py $(OBJDIR)/all.dep dbcsr $(MODDEPS) $(MAKEDEPMODE) $(ARCHIVE_EXT) $(SRCDIR) $(OBJ_SRC_FILES)
-
-# at stage 2, load the rules generated by makedep.py
-ifeq ($(INCLUDE_DEPS), true)
-  include $(OBJDIR)/all.dep
-endif
-
-
-# ================= Stuff need for compiling (stage 2) ======================
-# These rules are executed in a recursive call to make -C $(OBJDIR)
-# The change of $(CURDIR) allows to find targets without abs paths and vpaths.
-
-
-### Slave rules ###
-vpath %.F     $(ALL_SRC_DIRS)
-vpath %.h     $(ALL_SRC_DIRS)
-vpath %.hpp   $(ALL_SRC_DIRS)
-vpath %.f90   $(ALL_SRC_DIRS)
-vpath %.cu    $(ALL_SRC_DIRS)
-vpath %.c     $(ALL_SRC_DIRS)
-vpath %.cpp   $(ALL_SRC_DIRS)
-
-# $(FCLOGPIPE) can be used to store compiler output, e.g. warnings, for each F-file separately.
-# This is used e.g. by the convention checker.
-
-FYPPFLAGS ?= -n
-
-%.o: %.F
-	$(PYTHON) $(FYPPEXE) $(FYPPFLAGS) $< $*.F90
-	$(FC) -c $(FCFLAGS) -D__SHORT_FILE__="\"$(notdir $<)\"" -I'$(dir $<)' -I'$(SRCDIR)' $*.F90 $(FCLOGPIPE)
-
-%.mod: %.o
-	@true
-
-%.o: %.c
-	$(CC) -c $(CFLAGS) $<
-
-ifneq ($(ACC),)
-# if compiling CUDA/HIP backend
-ifneq (opencl,$(USE_ACCEL))
-%.o: %.cpp parameters.h smm_acc_kernels.h
-	$(ACC) -c $(ACCFLAGS) -I'$(SRCDIR)' $<
-# if compiling CUDA backend
-ifeq (cuda,$(USE_ACCEL))
-%.o: %.cu parameters.h smm_acc_kernels.h
-	$(ACC) -c $(ACCFLAGS) -I'$(SRCDIR)' $<
-calculate_norms.o: calculate_norms.cpp
-	$(ACC) -c $(ACCFLAGS) -I'$(SRCDIR)' -x cu $<
-acc_cuda.o: acc_cuda.cpp acc_cuda.h
-	$(ACC) -c $(ACCFLAGS) -I'$(SRCDIR)' $<
-# if compiling HIP backend
-else
-calculate_norms.o: calculate_norms.cpp
-	$(OFFLOAD_CC) -D__HIP -c $(OFFLOAD_FLAGS) -I'$(SRCDIR)' $<
-acc_hip.o: acc_hip.cpp acc_hip.h
-	$(ACC) -c $(ACCFLAGS) -I'$(SRCDIR)' $<
-endif
-
-# if compiling OpenCL backend
-else
-OPENCL_KRNLGEN := $(LIBSMM_ACC_ABS_DIR)/../opencl/acc_opencl.sh
-OPENCL_KERNELS := $(wildcard $(LIBSMM_ACC_ABS_DIR)/../opencl/smm/kernels/*.cl)
-OPENCL_DEFAULT := $(wildcard $(LIBSMM_ACC_ABS_DIR)/../opencl/smm/tune_multiply.csv)
-OPENCL_WITHGPU := $(wildcard $(LIBSMM_ACC_ABS_DIR)/../opencl/smm/params/tune_multiply_*.csv)
-OPENCL_PARAMS := $(if $(OPENCL_DEFAULT),$(OPENCL_DEFAULT),$(OPENCL_WITHGPU))
-OPENCL_COMMON := $(wildcard $(LIBSMM_ACC_ABS_DIR)/../opencl/common/*.h)
-$(LIBSMM_ACC_ABS_DIR)/../opencl/smm/opencl_kernels.h: $(OPENCL_KRNLGEN) $(OPENCL_KERNELS) $(OPENCL_COMMON) $(OPENCL_PARAMS)
-	$(OPENCL_KRNLGEN) $(OPENCL_KERNELS) $(OPENCL_PARAMS) $@
-opencl_libsmm.o: opencl_libsmm.c $(LIBSMM_ACC_ABS_DIR)/../opencl/smm/opencl_kernels.h
-ifeq (Darwin,$(shell uname))
-  LDFLAGS += -framework OpenCL
-else
-  # OpenCL include directory (cl.h not installed per "opencl-headers" package)
-  NVCC := $(shell which nvcc 2>/dev/null)
-  NVCC_PATH := $(if $(NVCC),$(realpath $(dir $(NVCC))/..))
-  CUDA_FILE := $(wildcard $(NVCC_PATH)/../cuda/include/cuda.h)
-  CUDA_PATH := $(if $(CUDA_FILE),$(abspath $(NVCC_PATH)/../cuda),$(NVCC_PATH))
-  CUDA_LIBS := $(if $(wildcard $(CUDA_PATH)/lib64),lib64,lib)
-  ifneq (,$(CUDA_PATH))
-    CFLAGS += -I$(CUDA_PATH)/include
-  else ifneq (,$(wildcard $(OPENCL_ROOT)/include/CL/cl.h))
-    CFLAGS += -I$(OPENCL_ROOT)/include
-  else
-    OPENCL_ROOT := $(abspath $(dir $(shell which icx 2>/dev/null))/..)
-    CLINC := $(wildcard $(OPENCL_ROOT)/include/sycl/CL/cl.h $(OPENCL_ROOT)/include/CL/cl.h)
-    ifneq (,$(CLINC))
-      CFLAGS += -I$(abspath $(dir $(firstword $(CLINC)))/..)
-    endif
-  endif
-endif
-endif
-endif
-
-$(LIBDIR)/%:
-ifneq ($(LD_SHARED),)
-	@echo "Creating shared library $@"
-	@$(LD_SHARED) $(LDFLAGS) -o $(@:.a=.so) $^ $(LIBS)
-else
-	@echo "Updating archive $@"
-	@$(AR) $@ $?
-endif
-
-#EOF
diff --git a/exts/build_dbcsr/check_archives.py b/exts/build_dbcsr/check_archives.py
deleted file mode 100755
index 8444514ee1..0000000000
--- a/exts/build_dbcsr/check_archives.py
+++ /dev/null
@@ -1,84 +0,0 @@
-#!/usr/bin/env python3
-# -*- coding: utf-8 -*-
-"""
-Check that a static archive contains only the objects specified in the PACKAGES files.
-"""
-
-# author: Ole Schuett
-
-
-import subprocess
-import os
-from os import path
-import argparse
-
-KNOWN_EXTENSIONS = ("F", "c", "cu", "cpp", "cxx", "cc")
-
-
-def main(ar_exe, src_dir, lib_dir):
-    # Search all files belonging to a given archive
-    archives_files = {}
-
-    for root, _, files in os.walk(src_dir):
-        if "PACKAGE" in files:
-            with open(path.join(root, "PACKAGE")) as fhandle:
-                content = fhandle.read()
-
-            package = eval(content)
-
-            archive = "libdbcsr" + path.basename(root)
-            if "archive" in package.keys():
-                archive = package["archive"]
-
-            file_parts = [fn.rsplit(".", 1) for fn in files]
-            src_basenames = [
-                parts[0] for parts in file_parts if parts[-1] in KNOWN_EXTENSIONS
-            ]
-
-            if archive in archives_files:
-                archives_files[archive] |= set(src_basenames)
-            else:
-                archives_files[archive] = set(src_basenames)
-
-    # Check if the symbols in each archive have a corresponding source file
-    for archive in archives_files:
-        archive_fn = path.join(lib_dir, archive + ".a")
-
-        if not path.exists(archive_fn):
-            continue
-
-        output = subprocess.check_output([ar_exe, "t", archive_fn])
-        for line in output.decode("utf8").strip().splitlines():
-            if line == "__.SYMDEF SORTED":
-                continue  # needed for MacOS
-
-            assert line.endswith(
-                ".o"
-            ), "discovered a non-object file inside a static archive"
-
-            if line[:-2] not in archives_files[archive]:
-                print(
-                    "Could not find source for object '{}' in archive '{}', removing archive.".format(
-                        line, archive_fn
-                    )
-                )
-                os.remove(archive_fn)
-                break
-
-
-# ===============================================================================
-if __name__ == "__main__":
-    parser = argparse.ArgumentParser(
-        description="""
-        Parse files and package manifests in the source tree to create rules for objects and executables
-
-        This script is part of the build utility scripts for DBCSR.
-        """,
-        formatter_class=argparse.ArgumentDefaultsHelpFormatter,
-    )
-    parser.add_argument("ar_executable", metavar="ar_executable", type=str)
-    parser.add_argument("src_dir", metavar="src_dir", type=str)
-    parser.add_argument("lib_dir", metavar="lib_dir", type=str)
-
-    args = parser.parse_args()
-    main(ar_exe=args.ar_executable, src_dir=args.src_dir, lib_dir=args.lib_dir)
diff --git a/exts/build_dbcsr/makedep.py b/exts/build_dbcsr/makedep.py
deleted file mode 100755
index c2e3c9f4ac..0000000000
--- a/exts/build_dbcsr/makedep.py
+++ /dev/null
@@ -1,441 +0,0 @@
-#!/usr/bin/env python3
-
-import re
-import sys
-import ast
-from os import path
-from os.path import dirname, basename, normpath
-import glob
-import argparse
-
-# pre-compiled regular expressions
-re_module = re.compile(r"(?:^|\n)\s*module\s+(\w+)\s.*\n\s*end\s*module", re.DOTALL)
-re_program = re.compile(r"\n\s*end\s*program")
-re_main = re.compile(r"\sint\s+main\s*\(")
-re_use = re.compile(r"\n\s*use\s+(\w+)")
-re_incl_fypp = re.compile(r"\n#:include\s+['\"](.+)['\"]")
-re_incl_cpp = re.compile(r"\n#include\s+['\"](.+)['\"]")
-re_incl_fort = re.compile(r"\n\s*include\s+['\"](.+)['\"]")
-
-
-# ============================================================================
-def main(out_fn, project_name, mod_format, mode, archive_ext, src_dir, src_files):
-    messages = []
-    # process arguments
-    src_files = [normpath(path.join(src_dir, f)) for f in src_files]
-
-    if mod_format not in ("lower", "upper", "no"):
-        error('Module filename format must be either of "lower", "upper", or "no".')
-
-    if mode not in ("normal", "hackdep", "mod_compiler"):
-        error('Mode must be either of "normal", "hackdep", or "mod_compiler".')
-
-    for fn in src_files:
-        if not fn.startswith("/"):
-            error("Path of source-file not absolute: " + fn)
-
-    src_basenames = [basename(fn).rsplit(".", 1)[0] for fn in src_files]
-    for bfn in src_basenames:
-        if src_basenames.count(bfn) > 1:
-            error("Multiple source files with the same basename: " + bfn)
-
-    # parse files
-    parsed_files = dict()
-    for fn in src_files:
-        parse_file(parsed_files, fn, src_dir)  # parses also included files
-    messages.append("Parsed %d files" % len(parsed_files))
-
-    # create table mapping fortran module-names to file-name
-    mod2fn = dict()
-    for fn in src_files:
-        for m in parsed_files[fn]["module"]:
-            if m in mod2fn.keys():
-                error('Multiple declarations of module "%s"' % m)
-            mod2fn[m] = fn
-    messages.append("Created mod2fn table, found %d modules." % len(mod2fn))
-
-    # check "one module per file"-convention
-    for m, fn in mod2fn.items():
-        if basename(fn) != m + ".F":
-            error("Names of module and file do not match: " + fn)
-
-    # read package manifests
-    packages = dict()
-    for fn in src_files:
-        p = normpath(dirname(fn))
-        read_pkg_manifest(project_name, packages, p)
-    messages.append("Read %d package manifests" % len(packages))
-
-    # check dependencies against package manifests
-    n_deps = 0
-    for fn in src_files:
-        p = normpath(dirname(fn))
-        if not parsed_files[fn]["program"]:
-            packages[p]["objects"].append(src2obj(basename(fn)))
-        deps = collect_include_deps(parsed_files, fn, src_dir)
-        deps += [
-            mod2fn[m]
-            for m in collect_use_deps(parsed_files, fn, src_dir)
-            if m in mod2fn.keys()
-        ]
-        n_deps += len(deps)
-        for d in deps:
-            dp = normpath(dirname(d))
-            if dp not in packages[p]["allowed_deps"]:
-                error(
-                    "Dependency forbidden according to package manifest: %s -> %s"
-                    % (fn, d)
-                )
-            if dp != p and "public_files" in packages[dp].keys():
-                if basename(d) not in packages[dp]["public_files"]:
-                    error(
-                        "File not public according to package manifest: %s -> %s"
-                        % (fn, d)
-                    )
-    messages.append("Checked %d dependencies" % n_deps)
-
-    # check for circular dependencies
-    for fn in parsed_files.keys():
-        find_cycles(parsed_files, mod2fn, fn, src_dir)
-
-    # write messages as comments
-    makefile = "\n".join("#makedep: {}".format(m) for m in messages)
-    makefile += "\n\n"
-
-    # write rules for archives
-    for pkg in packages.keys():
-        if packages[pkg]["objects"]:
-            makefile += """\
-# Package {pkg}
-$(LIBDIR)/{archive}{ext} : {objs}
-
-""".format(
-                pkg=pkg,
-                archive=packages[pkg]["archive"],
-                ext=archive_ext,
-                objs=" ".join(packages[pkg]["objects"]),
-            )
-
-    # write rules for public files
-    for pkg in packages.keys():
-        if "public" in packages[pkg].keys():
-            makefile += """\
-# Public modules for package {pkg}
-install: PUBLICFILES += {pubfiles}
-
-""".format(
-                pkg=pkg, pubfiles=" ".join(mod for mod in packages[pkg]["public"])
-            )
-
-    # write rules for executables
-    archive_postfix = archive_ext.rsplit(".", 1)[0]
-    for fn in src_files:
-        if not parsed_files[fn]["program"]:
-            continue
-
-        bfn = basename(fn).rsplit(".", 1)[0]
-        p = normpath(dirname(fn))
-
-        deps = collect_pkg_deps(packages, p)
-        assert all(a.startswith("lib") for a in deps)
-        cflagsvar = " $(LDFLAGS_C)" if fn.endswith(".c") or fn.endswith(".cu") else ""
-        makefile += """\
-# Program {fn}
-$(EXEDIR)/{bfn}.$(ONEVERSION) : {bfn}.o {deps}
-\t$(LD) $(LDFLAGS) {cflagsvar} -L$(LIBDIR) -o $@ {bfn}.o $(EXTERNAL_OBJECTS) {linkerdeps} $(LIBS)
-
-""".format(
-            fn=fn,
-            bfn=bfn,
-            deps=" ".join(["$(LIBDIR)/" + a + archive_ext for a in deps]),
-            cflagsvar=cflagsvar,
-            linkerdeps=" ".join("-l{}{}".format(a[3:], archive_postfix) for a in deps),
-        )
-
-    # write rules for objects
-    for fn in src_files:
-        deps = collect_include_deps(parsed_files, fn, src_dir)
-
-        mods = collect_use_deps(parsed_files, fn, src_dir)
-        mods.sort(key=cmp_mods)  # sort mods to speedup compilation
-        deps += [mod2modfile(m, mod_format) for m in mods if m in mod2fn.keys()]
-
-        if mode == "hackdep":
-            deps = []
-
-        deps = " ".join(deps)
-
-        bfn = basename(fn)
-        provides = [mod2modfile(m, mod_format) for m in parsed_files[fn]["module"]]
-
-        makefile += "# Object {bfn}\n".format(bfn=bfn)
-        for mfn in provides:
-            makefile += "{mfn} : {bfn} {deps}\n".format(mfn=mfn, bfn=bfn, deps=deps)
-
-        makefile += "{bfnobj} : {bfn} {deps}".format(
-            bfnobj=src2obj(bfn), bfn=bfn, deps=deps
-        )
-
-        if mode == "mod_compiler":
-            makefile += " " + " ".join(provides)
-
-        makefile += "\n\n"
-
-    with open(out_fn, "w", encoding="utf8") as fhandle:
-        fhandle.write(makefile)
-
-
-# ============================================================================
-def cmp_mods(mod):
-    # list "type" modules first, they are probably on the critical path
-    if "type" in mod:
-        return 0
-    return 1
-
-
-# ============================================================================
-def parse_file(parsed_files, fn, src_dir):
-    if fn in parsed_files:
-        return
-
-    with open(fn, encoding="utf8") as fhandle:
-        content = fhandle.read()
-
-    # re.IGNORECASE is horribly expensive. Converting to lower-case upfront
-    content_lower = content.lower()
-
-    # all files are parsed for cpp includes
-    incls = re_incl_cpp.findall(content)  # CPP includes (case-sensitive)
-
-    mods = []
-    uses = []
-    prog = False
-
-    if fn[-2:] == ".F" or fn[-4:] == ".f90" or fn[-5:] == ".fypp":
-        mods += re_module.findall(content_lower)
-        prog = True if re_program.search(content_lower) is not None else False
-        uses += re_use.findall(content_lower)
-        incls += re_incl_fypp.findall(content)  # Fypp includes (case-sensitive)
-        incl_fort_iter = re_incl_fort.finditer(content_lower)  # fortran includes
-        incls += [content[m.start(1) : m.end(1)] for m in incl_fort_iter]
-
-    if fn[-2:] == ".c" or fn[-3:] == ".cu":
-        prog = (
-            True if re_main.search(content) is not None else False
-        )  # C is case-sensitive
-
-    # exclude included files from outside the source tree
-    def incl_fn(i):
-        return normpath(path.join(dirname(fn), i))
-
-    def incl_fn_src(i):
-        return normpath(path.join(src_dir, i))
-
-    existing_incl = [i for i in incls if path.exists(incl_fn(i))]
-    existing_incl_src = [i for i in incls if path.exists(incl_fn_src(i))]
-
-    # store everything in parsed_files cache
-    parsed_files[fn] = {
-        "module": mods,
-        "program": prog,
-        "use": uses,
-        "include": existing_incl,
-        "include_src": existing_incl_src,
-    }
-
-    # parse included files
-    for i in existing_incl:
-        parse_file(parsed_files, incl_fn(i), src_dir)
-
-    for i in existing_incl_src:
-        parse_file(parsed_files, incl_fn_src(i), src_dir)
-
-
-# ============================================================================
-def read_pkg_manifest(project_name, packages, p):
-    if p in packages.keys():
-        return
-
-    fn = path.join(p, "PACKAGE")
-    if not path.exists(fn):
-        error("Could not open PACKAGE manifest: " + fn)
-
-    with open(fn, encoding="utf8") as fhandle:
-        content = fhandle.read()
-
-    packages[p] = ast.literal_eval(content)
-    packages[p]["objects"] = []
-    if "archive" not in packages[p].keys():
-        packages[p]["archive"] = "lib{}{}".format(project_name, basename(p))
-    packages[p]["allowed_deps"] = [normpath(p)]
-    packages[p]["allowed_deps"] += [
-        normpath(path.join(p, r)) for r in packages[p]["requires"]
-    ]
-
-    for r in packages[p]["requires"]:
-        read_pkg_manifest(project_name, packages, normpath(path.join(p, r)))
-
-    if "public" in packages[p].keys():
-        public_files = []
-        for fn in packages[p]["public"]:
-            public_files += glob.glob(path.join(p, fn))
-        packages[p]["public_files"] = [basename(fn) for fn in public_files]
-
-
-# ============================================================================
-def mod2modfile(m, mod_format):
-    if mod_format == "no":
-        return ""
-
-    if mod_format == "lower":
-        return m.lower() + ".mod"
-
-    if mod_format == "upper":
-        return m.upper() + ".mod"
-
-    assert False  # modeps unknown
-
-
-# ============================================================================
-def src2obj(src_fn):
-    return basename(src_fn).rsplit(".", 1)[0] + ".o"
-
-
-# ============================================================================
-def collect_include_deps(parsed_files, fn, src_dir):
-    pf = parsed_files[fn]
-    incs = []
-
-    for i in pf["include"]:
-        fn_inc = normpath(path.join(dirname(fn), i))
-        if fn_inc in parsed_files.keys():
-            incs.append(fn_inc)
-            incs += collect_include_deps(parsed_files, fn_inc, src_dir)
-
-    for i in pf["include_src"]:
-        fn_inc = normpath(path.join(src_dir, i))
-        if fn_inc in parsed_files.keys():
-            incs.append(fn_inc)
-            incs += collect_include_deps(parsed_files, fn_inc, src_dir)
-
-    return sorted(set(incs))
-
-
-# ============================================================================
-def collect_use_deps(parsed_files, fn, src_dir):
-    pf = parsed_files[fn]
-    uses = pf["use"]
-
-    for i in pf["include"]:
-        fn_inc = normpath(path.join(dirname(fn), i))
-        if fn_inc in parsed_files.keys():
-            uses += collect_use_deps(parsed_files, fn_inc, src_dir)
-
-    for i in pf["include_src"]:
-        fn_inc = normpath(path.join(src_dir, i))
-        if fn_inc in parsed_files.keys():
-            uses += collect_use_deps(parsed_files, fn_inc, src_dir)
-
-    return sorted(set(uses))
-
-
-# ============================================================================
-def find_cycles(parsed_files, mod2fn, fn, src_dir, S=None):
-    pf = parsed_files[fn]
-    if "visited" in pf.keys():
-        return
-
-    if S is None:
-        S = []
-
-    for m in pf["module"]:
-        if m in S:
-            i = S.index(m)
-            n = S[i:]
-        else:
-            n = []
-
-        if 0 == len(n) or (1 == len(n) and m in n):
-            S.append(m)
-        else:
-            error("Circular dependency: " + " -> ".join(n + [m]))
-
-    for m in collect_use_deps(parsed_files, fn, src_dir):
-        if m in mod2fn.keys():
-            find_cycles(parsed_files, mod2fn, mod2fn[m], src_dir, S)
-
-    for m in pf["module"]:
-        S.pop()
-
-    pf["visited"] = True
-
-
-# ============================================================================
-def collect_pkg_deps(packages, p, archives=None, S=None):
-    if archives is None:
-        archives = []
-
-    if S is None:
-        S = []
-
-    a = packages[p]["archive"]
-    if a in archives:
-        return archives
-
-    if a in S:
-        i = S.index(a)
-        b = S[i:]
-    else:
-        b = []
-
-    if 0 == len(b) or (1 == len(b) and a in b):
-        S.append(a)
-    else:
-        error("Circular package dependency: " + " -> ".join(b + [a]))
-
-    for r in packages[p]["requires"]:
-        d = normpath(path.join(p, r))
-        collect_pkg_deps(packages, d, archives, S)
-
-    S.pop()
-
-    if packages[p]["objects"]:
-        archives.insert(0, packages[p]["archive"])
-
-    return archives
-
-
-# ============================================================================
-def error(msg):
-    sys.stderr.write("makedep error: %s\n" % msg)
-    sys.exit(1)
-
-
-# ============================================================================
-if __name__ == "__main__":
-    parser = argparse.ArgumentParser(
-        description="""
-        Parse files and package manifests in the source tree to create rules for objects and executables
-
-        This script is part of the build utility scripts for DBCSR.
-        """,
-        formatter_class=argparse.ArgumentDefaultsHelpFormatter,
-    )
-    parser.add_argument("outfile", metavar="outfile", type=str)
-    parser.add_argument("project_name", metavar="project_name", type=str)
-    parser.add_argument("format", metavar="format", type=str)
-    parser.add_argument("mode", metavar="mode", type=str)
-    parser.add_argument("archive_ext", metavar="archive_ext", type=str)
-    parser.add_argument("src_dir", metavar="src_dir", type=str)
-    parser.add_argument("src_file", metavar="src_file", nargs="+", type=str)
-
-    args = parser.parse_args()
-    main(
-        out_fn=args.outfile,
-        project_name=args.project_name,
-        mod_format=args.format,
-        mode=args.mode,
-        archive_ext=args.archive_ext,
-        src_dir=args.src_dir,
-        src_files=args.src_file,
-    )
diff --git a/exts/build_dbcsr/test_makedep.py b/exts/build_dbcsr/test_makedep.py
deleted file mode 100755
index 7e76e72769..0000000000
--- a/exts/build_dbcsr/test_makedep.py
+++ /dev/null
@@ -1,255 +0,0 @@
-#!/usr/bin/env python3
-# -*- coding: utf-8 -*-
-"""
-Unittests for the makedep.py script
-"""
-
-import unittest
-import tempfile
-import shutil
-import json
-import io
-import os
-from os import path
-
-import makedep
-
-
-def _mkpkg(content, base_dir):
-    """
-    Create a PACKAGE file in the given directory.
-    If the content is a list or a dict, serialize the structure using json.dump.
-    """
-
-    with open(path.join(base_dir, "PACKAGE"), "w") as fhandle:
-        if isinstance(content, (dict, list)):
-            json.dump(content, fhandle, ensure_ascii=False)
-        else:
-            fhandle.write(content)
-
-
-class TestCheckArchives(unittest.TestCase):
-    """Test case for the main method in makedep"""
-
-    def setUp(self):
-        self.base_dir = tempfile.mkdtemp()
-
-    def tearDown(self):
-        shutil.rmtree(self.base_dir)
-
-    def test_empty_dir(self):
-        """
-        running on an empty dir with no files generates an empty deps file
-        """
-        my_dir = path.join(self.base_dir, "empty")
-        out_fn = path.join(my_dir, "all.dep")
-
-        os.mkdir(my_dir)
-
-        makedep.main(out_fn, "empty_project", "lower", "normal", ".a", my_dir, [])
-
-        with open(out_fn, "r") as fhandle:
-            no_comment_lines = [
-                l.strip() for l in fhandle if not l.startswith("#") and l.strip()
-            ]
-
-        self.assertEqual(len(no_comment_lines), 0)
-
-    def test_single_empty(self):
-        """
-        running on a dir with a single file
-        """
-
-        my_dir = path.join(self.base_dir, "single_empty")
-        out_fn = path.join(my_dir, "all.dep")
-        single_fn = path.join(my_dir, "single.F")
-
-        os.mkdir(my_dir)
-        with open(single_fn, "w") as fhandle:
-            fhandle.write("\n")
-
-        with self.assertRaises(SystemExit):
-            # should throw an exception due to missing PACKAGES
-            makedep.main(
-                out_fn,
-                "faulty_project",
-                "lower",
-                "normal",
-                ".a",
-                my_dir,
-                ["./single.F"],
-            )
-
-        _mkpkg(
-            {
-                "description": "Nothing",
-                "archive": "test",
-                "public": ["*.F"],
-                "requires": [],
-            },
-            my_dir,
-        )
-
-        makedep.main(
-            out_fn, "single_empty", "lower", "normal", ".a", my_dir, ["./single.F"]
-        )
-
-        with open(out_fn, "r") as fhandle:
-            no_comment_lines = [
-                l.strip() for l in fhandle if not l.startswith("#") and l.strip()
-            ]
-
-        self.assertEqual(
-            no_comment_lines,
-            [
-                "$(LIBDIR)/test.a : single.o",
-                "install: PUBLICFILES += *.F",
-                "single.o : single.F",
-            ],
-        )
-
-    def test_unicode(self):
-        """
-        running on a dir with a single file
-        """
-
-        my_dir = path.join(self.base_dir, "unicode")
-        out_fn = path.join(my_dir, "all.dep")
-        single_fn = path.join(my_dir, "single.F")
-
-        os.mkdir(my_dir)
-        with io.open(single_fn, "w", encoding="utf8") as fhandle:
-            fhandle.write(u"! Ångström\n")
-
-        _mkpkg(
-            """{
-    "description": "unicode test with just an Ångström 😉",
-    "archive": "test",
-    "public": ["*.F"],
-    "requires": []
-}""",
-            my_dir,
-        )
-
-        makedep.main(
-            out_fn, "unicode_project", "lower", "normal", ".a", my_dir, ["./single.F"]
-        )
-
-        with open(out_fn, "r") as fhandle:
-            no_comment_lines = [
-                l.strip() for l in fhandle if not l.startswith("#") and l.strip()
-            ]
-
-        self.assertEqual(
-            no_comment_lines,
-            [
-                "$(LIBDIR)/test.a : single.o",
-                "install: PUBLICFILES += *.F",
-                "single.o : single.F",
-            ],
-        )
-
-    def test_subpackage(self):
-        """
-        running on a dir with a single file
-        """
-
-        my_dir = path.join(self.base_dir, "subpackage")
-        out_fn = path.join(my_dir, "all.dep")
-        sub_dir = path.join(my_dir, "sub")
-        single_fn = path.join(my_dir, "single.F")
-        sub_fn = path.join(sub_dir, "sub.F")
-
-        os.mkdir(my_dir)
-        os.mkdir(sub_dir)
-
-        for fname in [single_fn, sub_fn]:
-            with open(fname, "w") as fhandle:
-                fhandle.write("")
-
-        _mkpkg(
-            """{
-    "description": "test with a simple subpackage",
-    "archive": "test",
-    "public": ["*.F"],
-    "requires": ["./sub"]
-}""",
-            my_dir,
-        )
-
-        _mkpkg(
-            """{
-    "description": "the sub package",
-    "requires": [""]
-}""",
-            sub_dir,
-        )
-
-        makedep.main(
-            out_fn,
-            "sub_pkg_without_dep",
-            "lower",
-            "normal",
-            ".a",
-            my_dir,
-            ["./single.F"],
-        )
-
-        with open(out_fn, "r") as fhandle:
-            no_comment_lines = [
-                l.strip() for l in fhandle if not l.startswith("#") and l.strip()
-            ]
-
-        self.assertEqual(
-            no_comment_lines,
-            [
-                "$(LIBDIR)/test.a : single.o",
-                "install: PUBLICFILES += *.F",
-                "single.o : single.F",
-            ],
-        )
-
-        with open(single_fn, "w") as fhandle:
-            fhandle.write(
-                """module single
-    use :: sub
-end module"""
-            )
-
-        with open(sub_fn, "w") as fhandle:
-            fhandle.write(
-                """module sub
-end module"""
-            )
-
-        makedep.main(
-            out_fn,
-            "sub_pkg_with_dep",
-            "lower",
-            "normal",
-            ".a",
-            my_dir,
-            ["./single.F", "./sub/sub.F"],
-        )
-
-        with open(out_fn, "r") as fhandle:
-            no_comment_lines = [
-                l.strip() for l in fhandle if not l.startswith("#") and l.strip()
-            ]
-
-        self.assertEqual(
-            sorted(no_comment_lines),
-            [
-                "$(LIBDIR)/libsub_pkg_with_depsub.a : sub.o",
-                "$(LIBDIR)/test.a : single.o",
-                "install: PUBLICFILES += *.F",
-                "single.mod : single.F",
-                "single.o : single.F",
-                "sub.o : sub.F",
-            ],
-        )
-
-
-# ============================================================================
-if __name__ == "__main__":
-    unittest.main()
diff --git a/exts/dbcsr b/exts/dbcsr
deleted file mode 160000
index 2cdbf1331e..0000000000
--- a/exts/dbcsr
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 2cdbf1331eb9f0e8265f4ca048cedb125f3e38f9