With the release of iOS 13.1 Apple will warn you via a prompt if you use a third-party screen. Apple claims this is to warn you of reduced functionality of the touch features on their new flagship phones’ displays.
While the warning itself doesn’t change the way the phone operates it will warn you of potential issues. The warning will be displayed on the lock screen for 4 days and within the settings for 15 after which you can find the prompt in General>About in Settings.
Read more about that here.