Okay do you want the good news or the bad news?
The good news is that you CAN install Virtualmin 7-RC8 fine on Ubuntu 22.04. The bad news is that there isn’t much point because there are literally no Virtualmin repos for it yet and it literally doesn’t set up any.
Wipe the system and install ubuntu 20.04 and use that for now (with the stable version 6.x installer).
You can upgrade Ubuntu in-place later it should be fine. Again there’s no problem with MariaDB… if that’s what you want just install it, I’ll test this in about an hour or so when I rebuild this particular VPS. 
The main benefit to 22.04 is it comes with OpenSSL 3.0, nothing to do with whether you can run MariaDB or not!!