It wasn’t too long ago when Apple was discouraging users to get unauthorised service repairs for their iPhone batteries, and now Apple is doing the same regarding its iPhone displays.
From iOS 13.1 onwards, iPhones including the iPhone 11, 11 Pro and 11 Pro Max will get a message that reads, “Unable to verify this iPhone has a genuine Apple display” if users choose to get their displays repaired by unauthorised service providers or technicians. This is because there are many risks and issues that could occur when unauthentic iPhone displays are used instead.
However, rest assured that if you still insist on going for third-party repair stores, your iPhone or display will still be functional i.e Apple will not block access to your iPhone or its display.