> if the KODI frontend is likely to work directly with the Digibit R1 instead of the TVheadend server?
It would be possible, but you would just have got access to the streams themselves, stuff like EPG, teletext etc. would not be possible
> I can use a RPi running LibreElec to watch live TV
LibreELEC offers the possibility to run TvHeadend as a server in the background and contains a PVR addon. So the Server would run on the same computer as the client.