Thanks for the information.
From a quick read of the AVR manual (PDF) it looks like the AVR supports TrueHD and dts-HD, but not Atmos.
It supports 4K video, but I did not see 4K HDR specifically mentioned.
Also, it supports HDMI-ARC, not HDMI-eARC.
If the AVR will passthrough 4K HDR video and you want TrueHD/dts-HD audio, then you’ve one clear option:
Nvidia Shield Pro ← HDMI → AVR ← HDMI-ARC → TV
HDMI-ARC cannot pass TrueHD or dts-HD audio due to bandwidth limitations.
Connecting the Shield directly to the AVR gets around the restrictions of HDMI-ARC.
If your AVR will not pass 4K HDR video (or you do not care about TrueHD/dts-HD audio), then use the Plex Android TV app on the TV.
TrueHD audio will be transcoded to another format. dts-HD audio might direct play, but pass only the lossy 5.1 core dts stream and discard the -HD part.
Other audio formats, AAC/AC3/EAC3/DTS/PCM, should direct play and be passed to the AVR, as HDMI-ARC supports those formats at 5.1 channels or fewer.
Note 1: The Plex Android TV app does not support direct playing of SSA/ASS subtitles. Enabling those results in a video transcode. PGS/VOBSUB/SRT subtitles will direct play, even if the video or audio is transcoding.
Note 2: TV manufacturers do not support passing TrueHD or dts-HD audio from TV based apps over HDMI-eARC. So, if you replace your receiver at some future time with one that supports HDMI-eARC, you will still need an Nvidia Shield, as the TV will not passthrough TrueHD/dts-HD from the Plex app on the TV.
This thread has additional information: [INFO] Plex, 4k, transcoding, and you - aka the rules of 4k
