XML and PLEX EPG's at the same time

The 00000 zip code trick was only during the initial release of PMS.1.23.1.4571 and maybe one or two versions after, right when Plex web was updated to 4.57.4.

If you want a mix of Plex EPG and XMLTV, you will need to do the web browser tab trick.
Open two web browser tabs of PMS> Settings> Live TV & DVR
On each tab proceed by setting up a DVR - have all tuners show in the pop-up. That’s it.
My personal preference is to set up my OTA first, so it auto-pins as that top Live TV & DVR library of the two.

I will point out that in versions beginning 1.23.1.4571 (the one where the new interface began), you will only see one DVR in Settings to manage, but both libraries will appear in the sidebar menu.
If you want to view and manage both DVRs, that last version to ever to do this is 1.23.1.4528, which I’m currently running.

I stopped frequenting the forums for about 2 months and stopped using Plex, but I am back. Prior to this I had tried about 3 Beta versions beginning with the newer interface on 1.23.1.4571, but always reverted back to 1.23.0.4497. Today, after updating to the latest version (1.23.6.4810), the mix of EPG data is still not there unfortunately. I downgraded PMS again.

Side note: don’t expect Enhanced Guide to work with IPTV, it stopped working when Plex went back to using Gracenote. Basically, no posters, no season numbering for shows.