When adding live TV tuners, the selection for EPG source (Plex or XMLTV file) is only allowed during the addition of the first tuner, and is then global for all tuners. I have two tuners and require one to use the Plex EPG, and one to use an XMLTV file. How can this be accomplished?
In my experience doing it you need a third party app that will combine the guides.
There is threadfin, and xteve that I know of. Otherwise you can run a second plex server just for the second tuner with the different guide.
Also, there’s a feature suggestion to allow both Plex guide data and XMLTV files, but it’s not very popular (9 votes in two years). You may want to vote for it:
I think there used to be some hack-ee ways to do this, such as opening two tabs to your Plex server and adding the two tuners at the same time. I have no idea if that still works and it certainly isn’t supported.
The best method, as @TheLivingBubba suggests, is likely to use a proxy tuner.