Last week I realized I could indeed play Atmos music in my current system without having to buy an Apple TV or any other additional hardware, it's possible to play Atmos mixes using the Tidal app in my Atmos-compatible LG TV through my Marantz Cinema 50. I don't have a full-fledged Atmos system, just a 5.2 system, but I find it works pretty well. Hence, I decided to end my subscription with Qobuz and switch to Tidal as I find the ability to play Atmos music adds to the overall experience as an addition to the regular 2-channel mixes.
I just did some testing on what will happen if I play an Atmos mix through my regular 2-channel streamer. I had hoped that the Atmos track would just be downmixed to stereo so that I would get the better dynamics of the Atmos mixes, but unfortunately, Tidal will only re-route the stream to the more dynamically compressed regular 2-channel mix when the playback system isn't Atmos compatible.
I'm not sure if Apple Music will also re-route the stream to the regular stereo mix just as Tidal does if you use a non-Atmos compatible playback system, so unless you have compatible gear throughout your system, I don't think you will get the less dynamically compressed version the Atmos mix is offering.
Oh by the way, why are you against changing to Tidal? Most of the MQA stuff is gone now when they are replacing them with regular flac files.