I never used Tvheadend before, I was able to make it work, including picons, but EPG seems to be an issue. Reading this forum and Tvheadend forums,it sems it is necessary to install a tv grabber like xmltv, a bit of complicated process.
Is there any improvement with Stretch is any guide show to do this on Stretch?
I think you can rely on the OTA EPG.
It’s been a while since I used xmltv, but I believe the process has been simplified a lot recently