Two issues with H6 HDMI audio were fixed - right channel not working and audio rate was not exact so audio was probably slightly distorted.
Please test following update and report if it works (valid for all H6 devices): libreelec-h6.arm-9.80-devel-20190914184226-e4aa9d6.tar
If it works, I'll PR changes to main LE repository.
Confirmed, with 1080p screen resolution sound is fixed and works fine, thanks a bunch for the effort. Please push it to the main.
A caveat though, with 768p screen resolution the sound problem persists (not so much a problem to me since I'm not using it.)