iPhone 8 devices that worked fine prior to the iOS 11.3 update have suddenly stopped working.
Last year, an iOS update killed touch functionality on iPhone 7 devices that had been repaired with third-party screens by independent repair stores. Patch notes for the update said that third-party replacement parts might not work correctly, but a week later another update resolved the issue. The message was clear: Software updates can kill core functionality on phones repaired by a third party.
This is a tough situation you want to wait for Apple to create a fix but you need your phone.