Usually you just need to change the domain on the GitHub side. We do mention this in the howto on changing your domain name – all social logins need to be changed to reflect the new domain.
We always associate logins based on email, so as long as the user logs in with the same email (either manually via click-the-emailed-guid-link, or automatically via a provider that sends a validated email) they will enter the Discourse account that matches that validated email.
Usually you just need to change the domain on the GitHub side.
Ah, bummer. What if the application has already been removed? Looks like I can at least hit the “Forgot password” and make a new password, assuming that’s because of this:
We always associate logins based on email
But I can’t hit the login with GitHub anymore as it’s still giving me the error.
We do mention this in the howto on changing your domain name