If your users rely on SMS Text Message or Phone Call for their Azure AD MFA authentication method be aware that Microsoft will start prompting them to register the Microsoft Authenticator App starting in September. Users will be able to skip the prompt 3 times by default but after that they will be forced to register.
You can control this behavior by changing the Registration Campaign settings in the Azure (Entra) portal. The state can be changed from Microsoft Managed to Enabled or Disabled, you can change the number of days allowed to snooze or exclude certain users and groups.
If you don’t have your users enabled for the Microsoft Authenticator app under Authentication Methods, they will not be affected by this September change. Also, if you are still using Legacy MFA your users won’t see the nudge.
This change was originally scheduled for July but was pushed back to September. For more information see Microsoft’s original announcement here: https://learn.microsoft.com/en-us/answers/questions/1307030/changes-to-the-registration-campaign-feature-in-az