I've tested this thoroughly before posting.
I have a 4K AppleTV linked to a brand new, high end Sony X90F via a Belkin ultra high speed cable. The pair can connect happily on 4K Dolby Vision 50hz, HDR and presumably all the lower settings too.
With the AppleTV on 4K Dolby Vision or 4K HDR, Infuse works fine so long as the video settings 'match dynamic range' and 'match frame rate' are set to OFF. When either of those settings are turned ON, I get a crash on playing a movie and the TV reports 'no HDMI signal'. It's as though the entire AppleTV has crashed, although the remote still seems to trigger the AppleTV's LED indicator and I can sometimes exit to the AppleTV main menu.
To be clear, this is NOT the normal brief change to black screen that happens when the AppleTV shifts video standard. It stays black. It doesn't come back no matter how long I wait.
Restarting the AppleTV doesn't work. Doing a full restart of the Sony TV (which runs on Android) DOES work for a while, but it flakes out again. I'm on the latest version of Infuse, TVOS and Android TV.
Also, in case you're wondering: I want to turn 'match dynamic range' and 'match frame rate' on for picture quality reasons. The video playback quality when left on default settings looks washed out and too low in colour saturation.