Transitioning from "Display Name or Email" to solely "Email" logins isn't seamless for users who have stored their login credentials using their Display Name.

They repeatedly click "Sign In" without comprehending the issue when login attempts fail.

Adding a simple tooltip to the login field when the entered value is not an email would greatly improve UX in this case. This way, users can easily see and switch without encountering further problems.

Example:

Also, it would be a good idea to keep the "Sign in" button in this form dusabled until both fields are valid (email is validated and password is not empty), so users won't waste their login attempts with this kind of little mistake.

Edited May 9, 20241 yr by 13.

It could even be smoother than that:

https://invisioncommunity.com/forums/topic/473885-feature-deprecation-discussion/?do=findComment&comment=2907946