None of your current clients support direct playing 4K HDR video and TrueHD audio passthrough. The only Plex client that does so is the Nvidia Shield.
Mac based clients do not support HDR video. HDR video will be tonemapped to SDR.
The LG Plex app plays 4K HDR video, but subtitles should be avoided as they can force a video transcode. Also, TrueHD and all dts audio variants will be transcoded.
I’m unsure of the capabilities of the Plex app on a PS4, but I’ve seen no posts saying it can passthrough TrueHD or dts-HD MA audio.
Regarding physical connectivity, if HDMI-eARC is enabled between the TV & Denon, you can connect the devices to either the TV or the AVR. If HDMI-ARC (not eARC) is used, then connect the devices to the AVR. eARC can pass lossless, high-bit rate audio such as TrueHD. ARC cannot due to bandwidth limitations.
See this thread for more info. It is long, but informative.
Additional Details:
Consider obtaining a Nvidia Shield Pro 2019. It is the only Plex client that will passthrough TrueHD + Atmos audio and supports 4K HDR video. Avoid the non-Pro “tube” model as it has issues with high bit rate media.
If Atmos is not a concern, then consider an AppleTV 4K or Roku. They send TrueHD as lossless PCM audio (Atmos data is lost during the process).
The LG Plex app will not pass dts-HD or TrueHD via HDMI-eARC due to LG hardware limitations. TrueHD and dts audio will be transcoded due to lack of codec support on 2020 LG TVs. The LG Plex app will transcode video when PGS, VOBSUB, or ASS/SSA subtitles are enabled. SRT subtitles + transcoded audio also forces a video transcode (so avoid TrueHD & dts audio).
Plex Media Player (on Mac or PC) does not support HDR video (it tonemaps HDR to SDR). PMP on a PC will passthrough TrueHD audio. I’m not sure about PMP on a Mac. Plex for Mac/Windows will have similar restrictions. Plex Web is more limited than Plex for Mac & PMP due to web browser restrictions.
I’m unsure of the capabilities of the Plex app on a PS4. However, I have not seen any posts saying it can passthrough TrueHD audio.
See this thread for additional details:
