The YouTube app on Android has recently allowed to play higher resolutions than the screen of the device can accommodate. Despite the fact that screens do not have the necessary pixels for this, they can still show a quality improvement due to the higher bitrate.
In addition to being able to choose a higher resolution, it is now also stated that hdr is used on non-hdr displays, although that will not provide any advantage. Android Police claims that all devices everywhere have been given the option. The change appears to have been made on the server side, as GSMArena sees the option on a version released early this month.
On iOS and desktops it was already possible to choose a higher resolution than the display; on desktops this has been the case for years and on the Apple side it has been possible since iOS 14, dating from September last year. Remarkably enough, YouTube introduced the temporary measure less than a year ago that videos on the platform were displayed in SD by default. This is due to increased use due to lockdowns.
Entering the option does not guarantee success, however; phones that simply cannot process that amount of data at that speed will experience dropped frames, causing the video to stutter.
Screenshot taken on a Pocophone F1, with a display resolution of 2246×1080 pixels