I ended up purchasing the Apple TV 4K and directly plugging it to the Denon and using the Infuse App. I know I don’t get Dolby Atmos, but I do get Dolby TrueHD & DTS HD-MA.
I would plug it to the LG, but there is a bug where LPCM higher than 2 channels don’t pass-through eARC to the Denon.
Have you got any more info on this? It’s very disappointing if it’s the case that LG won’t permit the high end audio codecs from internal apps - it’s literally the main reason for me buying a C9!
If it at least outputs upsampling Atmos/Neural X then that’s something but I was really hoping to get by with the internal Plex app only!