If you've had the screen repaired on your iPhone 8 by anyone other than Apple or an Apple authorized repairer, you should probably hold off on upgrading.
The screen will display the iOS home screen, but is unresponsive to touch input.
Third-party repair shops are up in arms about this move.
"This has caused my company over 2,000 reshipments," Aakshay Kripalani, chief executive of repair shop Injured Gadgets told Motherboard. "Customers are annoyed and it seems like Apple is doing this to prevent customers from doing third-party repair."
This is strikingly similar to the "Error 53" issue that iPhone 6 users who had the Touch ID sensor replaced by third-party repair shop were experiencing following the release of iOS 9. Apple did later push out an update to address the issue.
Apple has yet to comment on this issue.
In the meantime, if you suspect that your iPhone 6 has had its display replaced by anyone other than Apple (or an Apple authorized repairer), then I recommend holding off installing iOS 11.3 until Apple has a chance to comment and fix the issue.