How to share authenticate information with other OAuth provider?

Hi, as the title says, I want to connect Hubs with another website to achieve Single-Sign-On.

My purpose is to provide users to sign-in at once, use our system & hubs with only one-time registration or signing in.
I feel reticulum is independent by Hubs. So I think we can connect with other systems. (with internal API? or OpenID Connect?)
It's okay to use reticulum as a primary user information datastore, or use another system and use its information by reticulum.

I'm a newbie of Hubs/Reticulum, but I understand about general API/OAuth/OpenID. Could you give me some advice about this?

No files, tests, or entry points are named. First clarify whether Reticulum should be the primary user store or consume an external OAuth/OpenID Connect provider, then establish an agreed SSO scope and acceptance criteria before implementation.

Written by the indexing model from the issue text.