I use Channels with the TVEverywhere beta feature and I am using SlingTV with it and it works great. It pulls in my OTA channels, plus my sling channels in to one big guide and I can record straight to my Plex library. Here’s how I do it.
I have my channels DVR storage as the same folder as my Plex TV shows folder. Yes it’s 2 separate interfaces I have to manage, but it gives me the best of both worlds.