Discussion forked from original location at Multiple Ghost sites with ghost-cli on same server - #11 . Apologies for any discontinuity that may have resulted.
You can read what the Ghost team said about MySQL vs MariaDB and compatibility issues about two years ago: Ghost 5 + MySQL 8, what specific functionality?
Paraphrase: Small team, can’t support multiple databases. Since Ghost uses knex for database access, contributions to knex that maintain and improve knex support for MariaDB would be a good approach for users who want MariaDB compatibility.