linux FAHControl has some python dependencies, which causes issues with new U20.04 and U22.04 installs. There is a github version of FAHControl which will run on U20.04 and also a snap which will run FAHControl on U22.04.
My farm has been on U1804 desktop for past few years, but recently started upgrading the hosts to U20.04 desktop using live update/upgrade and existing FAHControl still runs OK.
Tried fresh U20.04 install using github FAHControl, but did not like having to start FAHControl from a terminal. Tried fresh U22.04 install without FAHControl, using FAHContol on my windows laptop to control the linux host, which works, but not as convenient as running on the actual host.
Made a fresh U18.04 install with FAHClient and FAHControl, then live updated to U20.04, and existing FAHControl still worked. Then live updated to U22.04 and existing FAHControl still worked.
My suggestion would be to make fresh U1804, get everything working, then live update/upgrade to U20.04.