problem

With MariaDB 12.1 the automatic naming schema of foreign keys did change what led to problems on updates.

solution

In the DB Updater implement a check to find out table creations with foreign keys or single FK creations where no explicit name was given. Could be similar to 

the 

if (str_contains($sql, 'DEFINER=')) { 

check in \ZfExtended_Models_Installer_DbUpdater::executeSqlFile

legacy code

Also we have to change several DB migration files back to 7.? version (we have to check what is out in the wild) and change the FK creations there to use the explicit name as it would have be done by MariaDB 12.0 to prevent follow up errors)