Custom CMS Update to support MariaDB

I have a small website that users can no longer sign up to and also some pages are giving 500 errors. After doing a little digging it seems it might not be compatible with MariaDB or might not be compatible with version 10.5 of MariaDB. This website was custom and done a few years back.

Looking for someone to come in and fix it. If it can get fixed then we may want to add some features as well.

Let me know WordPress ...