Ok, here's what I have tried so far.
Installed the build with the correct device tree. The installed tvheadend 4.2 using zip install. SSH remote.conf to make the remote work.
On the Tvheadend web interface I enabled availink avl6862 tvb t device. Added a network using Australia Melbourne (tried generic as well)
Went back to devices and selected the network on the device. Force scanned the network which always returns a failed status for all mux.
Tried this entire procedure on 8.0 c , 8.0 e and now on 8.1 as well.
One observation is that while scanning the status on the device shows signal strength in 90%+ however SNA is always 0. Is that why the scans are always failing? Is there an issue with the firmware? Btw I have tried scanning channels on TV and on the android DTV app both work flawlessly so there are definitely no issues with the antenna signal.
There is more help on the Kodi forum, Setting up an easy Linux Kodi with Live TV (LibreELEC)