I have a Azure sync issue for a user due to it has other language character (for examplw German's ü) we tried to change character to u instead of ü, however we got an below error,
The specified user logon name already exists in the enterprise. Specify a new one, either by changing the prefix or slecting a different suffix from the list.
Tried find the user with character u (we thought there is another user with this name already) and ensured that, there is no such user(s).
Seems the Windows OS settings could not identify the both characters are different and it always says above error.
Also tried customer LDAP query and result display only affected the user.
(&(objectCategory=person)(objectClass=user)(sAMAccountName=logumm))
So, we tried to rename the user with random number, like logümm121 and renamed to logumm. It works fine and AAD synced the user to Azure portal.