When restoring a user and selecting With object, you may wonder what happens if the user already exists in Entra ID.
In case the user already exists in Entra ID, a new user will not be created during the restore. Only the user attributes are restored, together with memberships and role assignments (if they were selected to be restored).
So there is no situation where a duplicate user would be created - unless you select 'As new' when a new user with a new Object ID will be created. But in this case the user needs to be given a new name, as a part of the restore options.