The intent was to retrace CPM’s steps in this thread
but this didn’t deliver desired results. Attempting to load a modified EDID (inject TV EDID while going through AVR)
echo load ~/edid.txt > edid
does not appear to make a difference - EDID does not seem to change and as Portisch pointed out a reboot may be required for this to be picked up. I don’t have enough understanding of CoreELEC and 4.9 kernel to follow along what CPM did here…
I have since run into other issues with DV playback on the device (unrelated to this one) and am putting this on hold for now, falling back to HDR10. Good luck and hope you have better success.