iPhone XS display has faint white horizontal lines
Why there are faint horizontal lines on my iPhone XS screen when the brightness is set all the way down in a dark room at night??
iPhone XS, iOS 12
It looks like a screen issue, but we can't diagnose it remotely.
Since your device is still covered by warranty, have it inspected at an Apple STore or Authorized Service Provider. After checking it out, they'll give you all the available options:--> Apple – Location Selector
Regards
Giulio