Comment 8 for bug 2031367

# My only theory is that, maybe, you happened to run an `apt update` in a weird situation where the Packages file for main (where linux-nvidia lives) was ahead of the Packages file for restricted (where linux-modules-nvidia-535-server-nvidia lives) on your mirror. I suspect that if you ran `sudo apt update; sudo apt dist-upgrade` and rebooted, your discrete video would recover.

that, or a mirror one is using did staged updates and has main quicker than restricted.

But strictly speaking on the packaging level there is nothing today that enforces strictly correct ordering of installing the right kernel modules for the currently booted kernel; nor installing modules for all the installed kernel abis. As the install of a new kernel flavour, or install of a given nvidia-drivers doesn't force the upgrade of the other, nor requests / indicates that a system reboot is required.

Ideally one should not use apt to install nvidia modules, as that doesn't ensure that matching userspace (if needed) is installed.

Please instead use `sudo ubuntu-drivers --gpgpu install` as that one likely to do the right thing, than hand invocations of apt. Similarly there is ubuntu-drivers integration to do something like that via cloud-init & autoinstall.yaml too.