My desktop booted with super low resolution (640x480) after upgrading from Ubuntu 18.04 to 20.04. I happily solved the problem following here. Software & Update > Additional Drivers > select the newest one, 450 in my case.

3行で nvidiaのドライバを削除 cuda関係のファイルを削除 再インストール 経緯 ubuntuのパッケージマネージャでupgradeをした時に，nvidiaのドライバをupgradeしてしまったっぽく，pytorchでcudaを使った処理ができなくて困った． (実は未だに)状況を完全に…

This post describes how to install an NVIDIA driver on Ubuntu 18.04. The official CUDA toolkit documentation didn't work me. I tried package manager based installation and it worked. Step 1. Disable the Nouveau driversNvidia driver install…