[noggin]

NVIDIA Shield:
- does auto Refresh switching in Plex/Kodi/SPMC only
- does auto Resolution switching in SPMC 17.6a2 only
- broken auto Colorspace switching Rec.709 (SDR) <--> BT.2020 (HDR) after auto Refresh switching.
- broken deinterlacing for OTA TV viewing with Kodi Krypton.

Isn't it a case that rather than colour space switching being broken on the Shield TV, it simply isn't implemented in either Kodi/SPMC or the nVidia Android TV builds at the moment ?

The Shield TV lets you manually select between a fixed Rec 709 and Rec 2020 colour space output, and Kodi/SPMC will then refresh rate switch within this colour space (and apparently also resolution switch in newer SPMC builds).  I haven't checked - but I assume if you run your nVidia Shield TV in Rec 709 3840x2160 HDMI output then Rec 2020 Netflix/Amazon content isn't properly converted currently, and conversely if you run 3840x2160 Rec 2020 HDMI output then Rec 709 stuff isn't either?

Given that TVs themselves only have a single native colour space - which is effectively defined by their display primaries (isn't it?) - there has to be a colour space conversion at some point.  Colour space switching the video output lets the TV do it all, but it is equally possible to do a Rec 709 to Rec 2020 colour space conversion within an app (or the OS - which might be cleaner if implemented properly)? which would then avoid the need for output colour space switching? (We're already doing this for 601 content - though the conversion is easier as it is often assumed the primaries and EOTF/gamma are the same)

Note colour space switching is separate to HDR / SDR - though almost all HDR content we will find is going to be in Rec 2020 colour space (or one of the DCI-P3s within it?) - as Rec 2020 stuff can be SDR (or SDR-compatible HLG)