Apple added a new feature in iOS 13.1 that alerts iPhone 11, 11 Pro and 11 Pro Max owners when a repair shop has installed a non-genuine display on their device.
In a support document detailing the new warning feature, Apple explains why you should only seek support from technicians who have completed training from Apple and use genuine Apple parts. Of course, Apple parts can be more expensive than knock-off displays, but using the cheap stuff could cause issues with multi-touch, display brightness and colors.