Yeah if there is only one way to login we bypass a screen so you don’t have to “click” and then “click” when logging in.
Our default https://github.com/discourse/discourse-oauth2-basic supports a lot of stuff, but is not as rich as SSO. So it depends on how much information you want to drive from oAuth2.
If basic is not good enough you will need to build another custom plugin to fish out the rest of the fields or do a PR to our official basic plugin.