[mike22]

Among other things that have been incompatible for a while: - many system tables use the Aria engine; has been impossible to start a MariaDB server over a data directory created in MySQL for many versions - mysql.user table has some completely different columns and authentication plugins diverged greatly as of MySQL 8.0, ie no caching_sha2_password (makes writing a user migration script challenging) - Even the data dir initialization scripts/programs are very far removed