I just ran apt upgrade on my Bullseye system upgrading to kernel 5.9.0-1 and got what looks like largely the same errors, but for nvidia-driver 450.66-1.
- Bug#972468: nvidia-graphics-drivers-legacy-390xx: module b... Vincent Lefevre
- Bug#972468: nvidia-graphics-drivers-legacy-390xx: mod... Ben B. Bainton
- Bug#972468: nvidia-driver 450.66-1 Markus Steinko
- Bug#972468: Error! Bad return status for module build... Markus Steinko
- Bug#972468: nvidia-graphics-drivers-legacy-390xx: mod... Thierry B.
- Bug#972468: nvidia-driver 450.66-1 Vincent Lefevre
