Change subtitles on Apple TV?
Slide down with one of your fingers inside the area representing the touch surface in the Remote app on your iPhone and a menu including Info, Subtitles, etc. should appear at the top of the video playing on the Apple TV.
Move to Subtitles using the touch surface in the app again and move onto and tap on any of the subtitle options that would appear. If the menu at the top of the video does not disappear after choosing a subtitle, tap on the MENU button in the app so that the menu at the top of the video disappears.