Probably this https://packages.ubuntu.com/focal/xserver-xorg-video-amdgpu for your AMD GPU ?
Linux firmware https://packages.ubuntu.com/focal/linux-firmware
You might look in « software & updates » [ = run software-properties-gtk from a terminal ] see if anything shows in the 5th tab, « Additional drivers ».
And finally a recent how-to https://linuxconfig.org/amd-radeon-ubuntu-20-04-driver-installation
Beware amdgpu-pro driver is not available yet for Ubuntu 20.04.
Am just gathering some information here, I have no AMD GPU to try by my side, hope it will help !
…from a French dude writing in English to a Spanish reader 
This is the bright side of internet !