Somewhat tangential, but here's a cool somewhat open-source project related to Dolby Atmos:

https://cavern.sbence.hu/cavern/

https://github.com/VoidXH/Cavern

The visualizer, which is what I was _most_ interested in (along with software decoding) is written in C# and the rendering is done in Unity -- both things I valued & thought were cool. In theory, you could build a DIY multi-channel "receiver" with this type of software if given enough audio outputs (and/or put something like Dante to use).

I explored it a bit further but it's relatively cost prohibitive, especially if you want to do something like accept HDMI input, it gets messy. AFAICT, at least when I went down this research path a few months back, even finding & getting dev kits/boards with HDMI input (of semi-recent generation) was non-trivial & pretty pricey.