nvidia – 20.04 reverts to Nouveau

So my son is running 20.04 Studio on his desktop – an older i7 with a GTX 750. The display reverted to 640×480 without a clear reason. He claims he had not run any updates recently nor installed any software, so it’s not clear what may have triggered it.

I took a quick look and noticed his display driver had reverted to Nouveau. Selecting the latest Nvidia driver seemed to install without issue, but made no difference, even after rebooting.

It’s not clear what’s caused it, but I see at least one other post describing this same problem in the last few days…