Subtitles / Closed Captioning

I’ve searched the forums and documentation but cannot get a straight answer so hopefully this will help.

How do I get cc / subtitles to work.
My recording has subtitles in it, (recorded via a HDHomerun, playing with VLCPlayer or even the HDhomerun app they show fine)
Mediainfo shows a EIA-608 text stream
However, the info screen in Plex Web shows: SUBTITLES None

Playing the file on my Roku 4, Galaxy S8 and casting to Chromecast, there is no way I can get subtitles to show.
However when I play from my iPad in the Roku app, the playback settings show a ‘CC’ option in subtitles et voila, I have subtitles.
Now when I cast to a Chromecast from the iPad Roku app they disappear again.

I’ve been through all the settings and they are as recommended, but the only device I can get it to work on is my iPad, defying all logic.

Who can shed some light on this?

Thx
Erwin

I am just responding because I can’t see a way to simply follow this question, and it needs to be addressed. I know as of 7 months ago or so the functionality for captions didn’t exist with the DVR, but I can’t find any information on if it is available now, and I can’t find an ETA or anything else. I’m fairly deaf so captions are vital.