Comment 8 for bug 1873597

REJECT for Xenial.

RE: Using the Ubuntu backported Galera 4 package would assure a good quality of packaging instead of using any alternative option, since the backported version is the same as the best one in Debian/Ubuntu at any given time.

This is true if and only if you are also backporting MariaDB in -backports as well. Any third party repository will by its nature not necessarily have a good quality MariaDB package, galera-4 aside.

So, curiosity begs the question: is there any intention here to also backport MariaDB?