screen orientation
Change screen from wide angle to regular.
iPhone XR, iOS 12
Question marked as
If the screen doesn't rotate on any app, it may be locked. Open Control Center by swiping down from the upper right corner of the screen and then tap the control that looks like a lock surrounded by a semicircular arrow. See: Use and customize Control Center on your iPhone, iPad, and iPod touch - Apple Support
Note that the home screen on an iPhone XR (and other non Plus size models) does not rotate and some apps do not rotate.