Login Selection for MySQL

Our web site uses MySQL to store login credentials among other things. Would it be possible to have a login that would use our database in addition to the other login selections provided by Discourse?

This is why SSO exists, search for SSO.

My understanding is that Discourse SSO does away with the other sign in options. Our MySQL database is for licensed Ham Radio operators only. But the Mailman List allows anyone to join. We want to keep that functionally if the list moves to Discourse.

That’s true, SSO is “magic login”. If you prefer multiple login options, including your own, then you need to write an oAuth 2.0 provider.