Well it’s dash/mp4 so Plex has to either
- Send the video via different means (e.g.
http/mkv) - Embed the subtitles into the video stream (e.g. CEA-608)
- Embed the subtitles into the DASH container (e.g. ISO/IEC 14496-30)
- Convert the subtitles into a compatible IMSC1 file (e.g. TTML XML)
That’s what I meant by “extra effort” – this will require some work but I think it will be worth it. Although in my particular case MKV should be enough and my TV definitely supports it (tested via USB drive).