From what I gather, the difference between "free" MariaDB and enterprise MariaDB, is solely around certification, support, and plugins. Is this correct? Is the server itself identical in these two instances?
MariaDB comes in a few different forms:
MariaDB is free and includes: Access all the features of MariaDB Server
MariaDB Enterprise Subscription includes a number of other features and is priced per server.
To look at the high-level features available see: https://mariadb.com/pricing