I had MySQL installed and running. I created some users using HeidiSQL, a Windows MySQL GUI and verified that they worked. I then upgraded to MariaDB.

Only my root accounts worked on MariaDB. When I checked the mysql.user table, the root accounts had empty `plugin` fields, but the non-root accounts had mysql_native_password in the field. Emptying the field and restarting the server (probably flushing privileges would have worked) resolved the issue.

I am not sure what was in the field prior to the MariaDB migration, but after checking all the other servers I have that are running vanilla MySQL, it was probably blank. I use HeidiSQL to create all of those users and none of them have a populated plugin field .