We might want to consider integrating this draft recommendation in the solid auth spec: https://openid.net/specs/openid-connect-prompt-create-1_0.html as it would be especially useful for Solid.

Traditional OIDC presupposes that a user is already registered with an IDP before the login process begins. However, with solid, a user might want to use a solid-compatible application without ever having registered with a solid-compatible IDP.

It would be useful to allow app developers to provide a "register" button that initiates the login process beginning with a registration flow rather than a login flow.