Bug#1079569: Had the same bug on my side. I think I discovered exactly what causes it.

[Whatthesac]

So when I installed the nvidia-driver package with nvidia-kernel-dkms,
everything worked fine but when I switched to nvidia-open-kernel-dkms,
Debian 12 wouldn't boot and it would stay on the screen with all the
"[ok]"s on it without doing anything, I pressed ctrl+alt+del on that screen
to open the terminal and looked at the logs with dmesg with grep "nvidia"
and compared that to the logs of a working system with nvidia-kernel-dkms
and I noticed these lines weren't there on the working system logs:

[ 17.039871] NVRM: Open nvidia.ko is only ready for use on Data Center GPUs.
[ 17.039874] NVRM: To force use of Open nvidia.ko on other GPUs, see the
[ 17.039874] NVRM: ‘OpenRmEnableUnsupportedGpus’ kernel module parameter
described
[ 17.039875] NVRM: in the README.

I then typed this command I found online:
echo "options nvidia NVreg_OpenRmEnableUnsupportedGpus=1" | sudo tee
/etc/modprobe.d/nvidia-openpm.conf
to force the use of open nvidia.ko on other GPUs than Data Center ones and
rebooted the system and everything worked flawlessly.

If I believe this line of log:
[ 17.039871] NVRM: Open nvidia.ko is only ready for use on Data Center GPUs.
The nvidia-open-kernel-dkms package present in debian 12 is still in alpha
and is not to be used for now. Maybe this page still holds true:
https://us.download.nvidia.com/XFree86/Linux-x86_64/515.43.04/README/kernel_open.html

If the nvidia-open-kernel-dkms package is effectively not ready to be used
on debian 12, I believe we should modify what this page
https://wiki.debian.org/NvidiaGraphicsDrivers says about the "open flavour"
of nvidia-kernel-dkms.

If you find there is a bit too much pride in this message you're probably
right 😅!  I'm a linux beginner (little experience on mint) and so I'm
pretty proud of myself for finding out what I just explained cause it's my
first time debugging a linux related issue 🙃!
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