@myhikingboots the cheapest method is a free trial through Tidal and the Firestick 4k, but your AVR has to be Atmos-capable. Mine wasn't (and is 5.1.2) but I did a software update and it works pretty well. Tidal doesn't have all of the releases that apple does (no beatles, pearl jam, or floyd).
Apple is $10/month plus the $180 for the ATV4K dongle thingie. As this thread shows, it's buggy based on the OS version (15.2 may still be buggy?) and whatever handshake is happening with the each listener's AVR.
Long story short, the future is here but it doesn't work very well yet!
I personally think spotify or someone else will swoop in with lossless atmos... or at least something better than what it is. Basically scalable dolby digital.