According to the documentation the Galera Manager can be installed on Ubuntu or AWS L2.
Incidentally, at this point, Galera Manager runs either Ubuntu or Amazon Linux 2. Future releases of Galera Manager may allow for other distributions of Linux.
This doesn't appear to be the case though, as the installer start by complaining about
WARN[0000] Debian / Ubuntu / Linux / focal / 20.04
and then asks a few questions before croaking with;
ERRO[0347] unsupported host os
I have tried 16.04, 18.04 and 20.04 without success. I haven't boot up an AWS instance as I don't want to run the GM in the cloud. Any thoughts/observations welcome.