You need to run a local m3u/epg proxy like xTeVe[1] to emulate a DVR. But you still need a Plex Pass I think.

[1] https://github.com/xteve-project/xTeVe

I built a thing that integrates with my ISP's TV API and makes it look to Plex like an HDHomeRun tuner. It also generates XMLTV EPG (again, based on my ISP's data) so that I don't have to faff around with third-party EPG providers and with channel matching.

So as far as Plex is concerned, this is an HDHomeRun tuner + XMLTV EPG.

I can also tune directly into any of the TV streams using VLC, in one of three ways:

1. raw MPEG transport stream over UDP multicast

2. same stream over HTTP (via udpxy)

3. my ISP's transcoded HLS stream (lagging by a few seconds and missing certain features)