Dear maintainers, tested a lot and I dicovered, there is a problem with the nvidia-package version 340.108-3-*.
This package (and even the original version from NVidia) does NOT build. However, on your repo I found version 340.108-10-*bpo*, which I manually downloaded and installed. This version is running well and I suggest, to release it as soon as possible. As I found a solution for me, I think, you can safely close this bugreport. Thank you very much for reading this and all the work. Best regards Hans