I ended up buying the Vertex2 device from HDFury. It solved all my audio issues by extracting audio from HDMI and sending it separately to my sound bar. Meanwhile, the video signal adds fake Dolby Vision support for my Samsung TV so that I get HDR whenever it’s available.

I do need to use Infuse as the media player on the Apple TV to get Dolby Atmos / Vision to work on most movies. I used to have to switch to the NVIDIA Shield to get that to work, but can’t remember a movie that has not worked lately.