Apple appears to have included a handy new feature in the latest iOS 15 beta release. As noted by @ShawnyRHarvey on Twitter, the Find My iPhone feature in iOS 15 beta 3 leaves the device findable, even after it has been powered off.
— Shawn H (@ShawnyRHarvey)
With iOS 15 beta 3, the iPhone remains findable using the Find My app when it has been misplaced, lost, or stolen, even when the device is in power reserve mode or when completely powered off.
Apple says this “Find My network” setting is enabled by default, and can be changed by going to Find My in settings.
Apple has also improved the redesigned Safari web browser in iOS 15 beta 3, introducing an updated address bar and a new reload button.