For Plex, I built a thing that exposes my ISP's multicast TV as an HDHomeRun-compatible tuner, with EPG. This works fairly well.
The main thing that's missing in this setup is support for DVB teletext subtitles in Plex. I end up having to post-process TV recordings to extract subtitles and convert them to SRT. This is all a bit messy, since we get TV from multiple neighbouring countries and there are often multiple languages and different teletext page numbers. Also, the timing tends of be out of whack. This means that the text needs to be re-synchronised with the audio; the thing I have generally works OK, but tends to fall apart when the audio in one language and subtitles, in another.
It would be all much simpler if Plex had the ability to show teletext subtitles when playing MPEG transport streams. Unfortunately, it doesn't.
I wonder if Jellyfin would be an improvement in this regard?