Ubuntu 20.4 LTS upgrade graphical glitches

Have you tried installing the correct drivers to the videocard? Or, alternatively if You already have the correct drivers; have you tried to go to software-updates (I think it's in the terminal called gtk-software-properties) and Checked there if you can choose (at the Drivers tab) some other Drivers?

related:

https://unix.stackexchange.com/questions/612018/ubuntu-20-04-problems-with-interface-after-installation

Edit:

I don't know if this will work; but if you're ok with re-installing gnome (As I said above: I am Not sure if this will work, so if unsure I would not try this, mainly because you can still access the desktop, somehow.)

however If you want to re-install gnome:

sudo apt-get install ubuntu-gnome-desktop

Ubuntu boots to black screen with cursor after upgrade (from 18.04 to 20.04)

The answer from:

Fuzzy graphics after upgrading to Ubuntu 20.04

sudo apt purge xserver-xorg-video-intel

"Reboot and everything is back being normal."

Edit2:

Related: Why is my monitor glitching out?

This has been solved another question.

sudo apt purge xserver-xorg-video-intel

followed by a reboot and everything is back to normal.