We have several web services, in addition, several Discourse for different audiences. For each service and related Discourse, Drupal 7 is now installed, which provides SSO for the service and Discourse. And such a pattern is repeated several times. The total number of users is more than 10 000.
I would like to create a single user base for all services and instances of Discourse. Make an SSO that provides transparent authentication everywhere. And at the same time get rid of Drupal.
The SSO system should not be cloudy, but located on our servers. Auth0, OneLogin are cloud systems.
So I ask for advice, what would I choose.