[noggin]

Thanks for detail explanation.
Can you list all the devices you owned?

Odroid C2, C4, N2
Raspberry Pi all models from original B and A to 4B and Zero 2W.
NVIDIA Shield TV
Apple TV 4K v1 and v2
Various x86 boxes
Amazon Fire TV sticks of various flavours
Google Chromecast with Google TV
(Also some Rockchip stuff)

So you actually tested 4k 10 bit HEVC HDR on your own google chromecast with Google TV, and it was playable but had the judder, 3:2 pulldown issue?

No - didn't bother - no way I'm watching fixed 60Hz output for anybody.

What do you think of going back to HTPC build?

I stopped building HTPCs in the HD h.264 era. Haven't built any custom boxes for UHD h.265.

Don't like Windows as an HTPC OS and Linux on x86/x64 isn't there yet for UHD HDR (apart from some custom x86 builds for some more recent Intel CPU+GPU SoCs)

At the moment I don't see much point in a Linux or Windows HTPC for my use case.

e.g. pi3b+ (no longer has hardware acceleration on kodi 19).

That's a very different kettle of fish. Kodi and/or LibreElec developers have taken a move to standardise video playback upstream and not support 50,000 lines of patches that won't ever be upstreamed (i.e. Pi3B+ HEVC decode support). That's just a move to ensure Kodi itself continues to be developed - and moves it to be more platform neutral.