I managed to connect GitLab and Microsoft (Azure) with this plugin. btw: for the Azure AD service, make sure to use the “Application Client ID” as client id, not the secret ID or value).
How is it possible to connect Discourse with two OIDC providers, e.g. GitLab and Azure?
EDIT: I managed to get GitLab Login working with OAuth2, so my question is now more “theoretical”.