Can I downgrade/upgrade from MySQL 8.0 to MariaDB? I no longer see a MariaDB option on the "Home >> SQL Services >> MySQL/MariaDB Upgrade" page in WHM.
Previously MariaDB was a drop-in replacement for MySQL, however changes that were introduced in MySQL 8.0 have made it incompatible with MariaDB. The following page from the MariaDB project's documentation provides more information about the compatibility between different versions of MySQL and MariaDB:
MariaDB versus MySQL: Compatibility - Drop-in Compatibility of Specific MariaDB Versions
There is not a supported way to perform a MySQL downgrade on a cPanel server at this time. If you need to use a specific version of MySQL you can use the following support article to setup a new server with that version:
How to customize the version of MySQL or MariaDB used when installing cPanel for the first time