I believe this is related to some recent changes in the latest versions of DBD::mysql that will limit new versions to only MySQL 8, so these new versions will not work with MySQL 5.7 and earlier, or MariaDB. For now, I think the easiest fix is to manually install an earlier version. The previous released version was DBD::mysql 4.052 which you can get it on CPAN. We will be looking at how to update the RT dependency checking to try to do the right thing based on the selected DB.