With my new server, the default installation came with MariaDB. Considering that cPanel supports migrating from MySQL->MariaDB within UI, but NOT the reverse, MariaDB should NEVER be installed by default.

MariaDB is NOT a drop-in replacement for MySQL, e.g.:
https://community.sugarcrm.com/ideas/1460

Furthermore, cPanel itself has backtracked on their MariaDB position and (reading between the lines) may stop supporting it at some point:
https://blog.cpanel.com/being-a-good-open-source-community-member-why-we-hesitated-on-mysql-5-7/

The decision to support MariaDB by default dates to ensuing uncertainty around the Oracle acquisition of MySQL nearly 10 years ago. As identified by cPanel, those fears didn't play out and MySQL is still a better choice than MariaDB for serious web applications.