I've just installed VirtualMin on a server where I wanted to run the latest MariaDB from the off. So I added the MariaDB 10.4 RPM repo before installing VirtualMin.
All went fine with the installation, but Step 5 of the Post-Installation Wizard offers to remove the test user and database, and forces you to set a root password for MySQL. That's a good thing.
Except that, when you click "Next", you get
update user set authentication_string = password('foo') where user = 'root' and host = 'localhost' failed : Column 'authentication_string' is not updatable
This is because of the note about MariaDB 10.4 at https://mariadb.com/kb/en/library/mysqluser-table/ meaning this is no longer the way to set passwords.
To work around, I tried setting a password at the commandline, but Step 5 doesn't detect this and says "Currently the MySQL password is not set, which is highly insecure."
So I tried not setting a password, even though it's "highly insecure", and I still can't progress because it then tries to set the empty password rather than skip the step.
I realise that MariaDB 10.4 is probably not officially supported yet, but 6 weeks in I thought it worth filing a bug report so that this gets picked up in due order.