You are welcome.
The only documentation that I am aware of is that no one of the thousands of plex users has found an E-ARC tv that will pass hd audio via built in app.
You (or anyone else) are free to prove me wrong, I would welcome it, and I am sure many others would love to find the perfect tv that does not need any other external device.
My belief is that the hdmi e-arc spec applies ONLY to physically connected HDMI devices, which does not apply to built in software apps, so that would mean the limitation is the hdmi/e-arc spec.
Until some manufacturer creates a tv that can utilize e-arc via app, we are all screwed.
this thread @ [INFO] Plex, 4k, transcoding, and you - aka the rules of 4k may (or may not) be of use to you, there is a whole ton of discussion regarding 4k and plex. Please read the entire thread.