Ubuntu 20.04 run fails when MariaDB is installed

[TheGuyDanish]

The current settings assume that default-mysql-client can always be installed, which is not the case. On Ubuntu 20.04, this defaults to mysql-client-8.0. Attempting to install this with a MariaDB server (or MariaDB client) installed will cause a conflict in apt and fail the run.

I'm currently looking into what possible ways there would be to patch this to either try and detect MariaDB in the environment, or allow a MySQL/MariaDB preference to be set in a variable.