There are no triggers for Active Directory in Power Automate. It isn't supported. The best you can do is create a scheduled flow that runs on a regular basis, grabs the current list of users and parse that list against a stored copy to look for new users. (Not sure, but there may be a way to get a list of users created in the last X time period. Not an AD expert). Regardless, no triggers exist, so you'll have to work around it a bit. It's still possible though. I've used the other approach with a couple of clients, storing a list of users in a database table or Sharepoint list to compare the most recent copy to.
