If you absolutely insist to have the latest AMD Radeon driver version you may use the PPA third-party repository which might be always ahead of the stable default opensource driver coming with your Ubuntu 20.04 system as default.

To install the PPA third-party repository drivers execute the following commands:

sudo add-apt-repository ppa:oibaf/graphics-drivers

The above will add the PPA AMD Radeon driver repository to your system. The following command will upgrade your current AMD Radeon driver to the latest version:

sudo apt update && sudo apt -y upgrade

In case you need to revert back to your original Ubuntu AMD Radeon drivers you can remove the PPA driver installation using the below commands:

sudo apt install ppa-purge
sudo ppa-purge ppa:oibaf/graphics-drivers