For verification I have installed Bookworm on an external SSD (using debootstrap), added Gnome and nvidia-graphics-drivers 525 and verified, upgraded to Testing and verified, and upgraded to Unstable and verified (still 525.147.05-7~deb12u1). X worked.
Next I cherry-picked nvidia 535.86.10-1 from experimental and tried again: Now its broken. Please note there is no xorg.conf Regards Harri