I need ID number for iPhone devices

Hello people, I wanted to get/create any ID number for Iphone devices, so that every phone can just use some feature for only one time based on if this ID is already there or not. even if the user reinstalled the app or whatever, it must stay the same. I know that we can’t use the IMEI for the ios devices so any help else?

It is tricky with the X platform without some login process.

You can use the LocalStorage to store a random variable. (LocalDB has a bug)
Make the variable at least 13 characters. That makes the odds of a match roughly 1 in 1,000,000,000,000

Then use that in firebase and you can cross reference the local id with the remote one.