darn it, just tell me what to buy.
I've heard the Sony system is good, but audio has to be encoded in Sony's format.
I used to own the Smyth Realiser 8 and it was awesome. The latest version is the 16. It's rather expensive, which is maybe why the source article didn't mention it, but you can feed it almost any surround sound source. It's probably the most versatile (and expensive) of the bunch:
To use a lighting to 3.5mm connection, I think you meant the AirPods Max, not the AirPods Pro. On that note, the AirPods Max have the same spatial audio support/restrictions as the AirPods Pro.