I seem to have the same issue. Upgraded from 11.0.6 to 12.0.1, after an succesfull upgrade procedure and a reboot, it results in a black screen. Tried LibreELEC-Generic-legacy.x86_64-13.0-nightly-20240826-7643d36.img with same result.
Fortunately i was able to downgrade to 11.0.6 , and now i'm able again to use my htpc.
My htpc specs: i3-8100 with 16gb ram, nvidia gt1030 gpu. Never had any issues with it before. Can this be fixed so i can use LE 12?