Hi Markus, I confirm that this is a serious issue.
I got the same error message Could NOT find Python3 (missing: Python3_INCLUDE_DIRS Python3_LIBRARIES Development NumPy Development.Module Development.Embed) (found version "3.9.0") in a completely different software project after I dist-upgraded my Debian/ testing system. That upgrade did not affect my cmake, which I compile myself (version 3.18.20200714-g2da7786-dirty). However, the upgrade did change numerous Python3 packages, among them python3-numpy:amd64 (1:1.19.1-1, 1:1.19.2-2+b1) but not python3-dev. So my guess is the problem is a change in python3-numpy that breaks CMake's find_package(Python3 COMPONENTS Development NumPy) command. Accordingly, I will report the bug to python3-numpy. Regards, Joachim
smime.p7s
Description: S/MIME Cryptographic Signature