You do realize Ubuntu MATE 20.04 LTS is End of Life
Further Ubuntu 20.04 LTS is End of Standard Support with Ubuntu support End of Life, with ESM provided only by Canonical.
This won't be an issue for you if you're keeping the system offline of course, but if you're using a network connection and/or internet, you need to take advantage of your Canonical provided support options if you took them up.
I hope you also read & actioned the Security Notices that applied to 20.04, and converted the deb packages that are now only supported via snap packages; as that impacted desktop users which applies of course to Ubuntu MATE (being a desktop system).