As I learned, I had to to this to prepare the kernel sources:
cp -rf include/generated/* include/linux/
After that, installing the NVIDIA..... .run file works fine (even without the need for using the "--kernel-source-path" or the "--add-this-kernel" parameters).
Thanks to the people who told me this solution via private message and bugtracking site. My fault. Didn't know about the prepare-kernel-sources.