“Requires username” feature is broken for custom database scenarios.
When using the custom database feature, with requires username selected, the feature is broken because the GetUser script (for user migration and forgot password/reset password flow) still gets passed an email (unlike the login script which is correctly passed a username). Since emails are not unique in our system (usernames are), this makes it impossible to identify the user performing the activity, which means we cannot provide a flow for the user to reset password using the universal login, and cannot migrate our users to auth0 db.
Using a custom database that has non-unique emails (because of multiple signins for multiple apps).
I see a lot of existing threads on this, but response is always “report feedback” - so here I am, reporting a known issue.