Hey,
I’m experiencing the same issue here. I have a Nextcloud instance set up as an OIDC provider, though that’s probably not relevant to the problem.
I can log in using my Nextcloud credentials. As described above, I’m then prompted to either register a new account or log in with an existing one. However, no link is established with the existing account via the email address.
If I select “Register,” I’m immediately redirected back to the homepage in a logged-out state, and I have to log in again. No error message is displayed.
That’s quite strange.
Everything works fine when I log in with an OIDC account that doesn’t have a matching Discourse account. In that case, a new account is created immediately, and the linked account also appears in the user settings.
Perhaps someone else has an idea about what I might be doing wrong, or it turns out there’s a bug after all.
Best regards,
Mike