Fetch Currently Logged in user on the App Store/Play Store without requesting authentication to the user for the UID to be used on that user's data

Currently I want to get the current user Logged in Data from the App Store/Play Store as the UID for the data to be used in that App.

Would this be possible without the need for authentication? Maybe in the startup or installation as it was said to be common in the App Development. As right now I can’t be sure what can be as the UID for the data of the user of the device so that it can be synced with the other devices.

What needs to be achieved: The Application must have it’s data synced with other devices that has linked to the same account other devices.

The requirement: The Application must not have any authentication and right now not ask any emails of the user.

As far as I know, Apple stopped sharing a real UID for the device years ago. You can get a device id from Device plugin but that id changes when you remove and reinstall the app.

Yes, I think this is Correct as well, though the device UID won’t be usable as the data should be in sync with other devices as such similar UID must be available.