[ashlar]

So what are the options for a box that can do 4K, HDR, 3D Frame Packing, HD audio passthrough, HDMI CEC and 23.976 Hz?
Apollo Lake and Kaby Lake both fail some of the above.

The ONLY thing that 'Does it all' is a Widows 10 computer of any type with an Nvidia GTX 960 graphics card or better as long as it hardware decodes, especially HEVC.
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Expect a resurgence in the HTPC market based on shortcomings of the streaming box fad or you can keep adding collections of them and fumble around constantly.
There's probably a couple worthless bells and whistles a streaming box offers exclusively. Personally, I'm only interested in the meat and potatoes, not the sauce.

Afaik, there is NOTHING else out there that can make the same claims. N O T H I N G. 

 I would agree with you and strongly support and wish the best for this scenario BUT... the streaming apps landscape is terrible. If you care about Netflix, Prime, etc... a Windows PC offers pretty much the worst experience possible. Which upsets me to no end.