Is there anyway to force subtitles on using an HLS+WebVTT to AVPlayer or MPMoviePlayerController, or any other video playback component?
Force Subtitles
You can select which subtitle track to utilize, if any, via the selectMediaOption(_:inMediaSelectionGroup:) method for AVPlayerItem.
Get the AVMediaCharacteristicLegible selection group from the AVAsset, investigate the available options, and then use the above method to select which subtitle option you would like to use.