User Profile Ramifications when Renaming Users on Azure AD-Joined Computers

I'm starting to work more with devices that are Azure AD-joined rather than domain-joined. One of my key questions was what happens to user profiles when an Azure AD user sign-in name (UPN) is changed. I was pleasantly surprised by how well it worked.

For my testing, I created an Azure AD user and signed in to create a profile. During sign-in, I created a PIN for authentication. While signed in, I also configured an Outlook profile and OneDrive. Then I tried changing the domain portion of the username and the userid portion of the username. The results were the same:

• I could still sign in with the PIN.
• I could sign in as the same user (username displayed on sign-in screen) with the password.
  
• I could sign in with the new username (typed in) and password.

After signing in:

• The workplace account was updated to the new username.
• Outlook was still able to sign-in without user intervention and updated the account.
  
• OneDrive continued to function without user intervention and updated the account.
• The same Windows 10 user profile was retained.