recently I upgraded from 19.10 to 20.04 LTS. Everything is working fine except some minor display issue. Display resolution if good but every time I turn on my computer or restart it, there is square green patches or vertical green lines over the wallpaper. Also, the moment I change the wallpaper it disappears. I don't what the exact issue is? I am using HP notebook. Below I have attached what it looks like.
I had similar issue when upgrading from Ubuntu 19.10 to Ubuntu 20.04 LTS.
I'm using Nvidia-prime with "On Demand" profile, so in fact still using the Intel graphic card for the desktop.
Solution was to remove the xserver-xorg-video-intel driver which is discouraged for hardware from 2007 and newer. Better to uninstall this driver and let the system use its builtin modesetting driver instead.
This can be done by the following command:
sudo apt purge xserver-xorg-video-intel
I found this solution there (as suggested in the comments by 0xC0000022L and karel): Ubuntu 20.04 graphics driver problem