I just got updated HGTV and Food Network apps that now have the "Live TV" option to get the live feed, instead of on demand only. This brings it up to parity with the Roku app.
Note: They still don't integrate with Live Channels unfortunately. Note 2: If you're on PS Vue the foodnetwork.com/androidtv is still missing an option to login with psvue, so you need to go to foodnetwork.com/roku to reactivate the app.
... but can you authenticate with Comcast?