So my TV has a roku built in which I'm extremely happy with. The only limitation is that, the Plex app can not pass True HD to my receiver via Arc.
From my research Nvidia shield directly plugged into my receiver can do it.
But Im not gonna use Shiled for anything else, like gaming and the 180 usd is a bit overkill.
Any other alternative? Does Mi Box support audio passthrough?
Any inexpensive Amlogic based Android box CAN and DOES support EVERY audio AND video codec. Here is my video comparing one of these inexpensive Android boxes running CoreELEC to the Nvidia Shield and a media player running on a Windows computer. You may be surprised at what an inexpensive device is capable of. This is a review of the Emby client, BUT, it works for the Plex server also.
You cannot passthrough HD audio via regular HDMI ARC or even SPDIF, it simply does not have the physical data transmission bandwidth to do so.
ARC can only do lossy 5.1 AC3 or lossy 5.1 DTS or 2.0 PCM audio.
The Original 2016 Mi Box, model MDZ-16-AB supports Kodi Leia HD audio passthrough via regular HDMI. The 2018 Mi Box S does not.