Hi there!
I use Infuse on the (still) current-generation Apple TV 4K, connected to an 83-inch Panasonic G5 OLED TV. I plan to play HDR slideshows encoded using HandBrake or Apple Compressor on the Apple TV through Infuse.
My question is: Can Apple TV with Infuse correctly decode and play video files encoded with 4:2:2 chroma subsampling, or is playback limited to 4:2:0?
ATV definitely. Don’t see the gain from 4.2.0 to 4.2.2 when using the suggested lossy tools.
My workflow roughly looks like this: I use a Hasselblad X2D II to shoot RAW photos, which I develop in Hasselblad Phocus with HDR and save as full-quality HEIF files. I then import the HEIF files into an HDR PQ timeline in Final Cut Pro, export the finished HDR video in ProRes 4:2:2 HQ, and encode it with HandBrake.
The question now is whether I should choose 4:2:0 or 4:2:2 in HandBrake. Up to that point, my workflow involves relatively little quality loss. It would be frustrating if the 4:2:2 file encoded with HandBrake ended up causing playback issues on the Apple TV.
Not trying to sound snarky but would it be that difficult to generate one of each and see which you think is best? Everyone has their own level of acceptability and you’d be the best to judge what you’re looking for. 
I should not worry about the ATV
But I would recommend the following setting:
OnOnIn theory yes, this will work just fine.
A bit of info I will share. It has been a little while, but last time we checked the Apple TV was sending a 10-bit video signal with the chroma set to 4:2:0 and a 12-bit signal when it was set to 4:2:2. Some TVs weren’t handling this 12-bit signal very well and there was some odd shadows and ghosting present.
In general, most all commercial videos are mastered in 4:2:0 chroma so setting this to 4:2:2 will not provide any additional benefit. If you’re creating your own videos there may be something to gain by using 4:2:2 but the caveat mentioned above could still come into play.