📝OpenID Connect can be used as a universal authentication system
OpenID Connect (OIDC) can be used as a universal authentication system.
With OIDC Discovery and OIDC Dynamic Registration, it allows websites (Relying Parties in OIDC terminology) to implement OIDC without pre-registering with any of Identity Providers and allows the user to select their own Identity Provider.
Self-Issued OpenID Provider specifications allows the user to authenticate without a third-party OP. This is very similar to GPG-based authentication.