I recently got a HDHOMERUN and have it all set up in plex. On my phone and on my computer live TV works just fine. On my Roku it works great but I have subtitles. I checked the TV settings and there off. I can’t seem to find any settings on the Roku in Plex to turn them off. IT also does this on every channel.
Under settings/server/languages i have subtitle mode set to manually selected.