I have installed Ubuntu 20.04 on two different desktop computers and encountered the same problem: the monitor is shown as "unkonwn display" and the resolution is fixed at 1024x768(4:3) and can not be changed, with my second monitor being not detected.
When installing, I opt to install all the non-free third-party drivers, so I expect the monitors should work out of box. I also installed Ubuntu 20.04 on two laptops, where the monitors work perfect.
My impression is that this version of Ubuntu is focused on laptops while has some obvious problems that can arise in desktop computers not taken care of.
Before posting this, I read the following question and all the answers: Ubuntu 18.04 Displays Issue -> Unknown Display
About 15 years ago, I often had hardware problems when I installed a linux distribution on various computers. This kind of problem seems to have disappeared in the last decade: hardware always work out of box. So I do not expect I need to manually install drivers for a particular device after a fresh installing. I think the hardware I am using is not weird enough that is unable to be automatically handled by the installer.
I tend to consider the above problem as a bug recently introduced in the ubuntu distribution
ubuntu-bug ubiquity
. We are not Canonical employees in here, we are only volunteers to help you if you need. – Terrance Mar 17 '21 at 03:50