At this time, only the iOS/TVOS based devices can decode Atmos streams and apply binaural transforms for the Apple AirPod line. The decoding ability is at the OS level, so any App could make use of that API to pass a DD+ encoded Atmos audio stream would get correctly processed for the headsets. For instance, the Tidal App for both the Apple TV and iOS can stream Atmos (I've used that).
The Netflix and Disney+ apps also do Atmos on the AppleTV, so it's not restricted to Apple-branded services.
As for Atmos on the macOS machines, I'm guessing they have not done anything there yet due to licensing. Technically, it could be done yesterday, so the fact that it has not been, tells me it's a business decision to not pay Dolby a royalty for every macOS machine on the planet.
As a Mac user myself (since 1984), I do not see that as a big deal, as each of my systems has an AppleTV, and I have an iOS device on or near me at all times to feed the AirPod Max or AirPod Pro headsets. So I sit at my desk and play stuff on Apple Music from my iPhone while wearing the AirPod Max headset. That way, if I get up and go upstairs for a drink refill, I don't miss a beat.
The sad part is I have a nice DAC + Amp + Electrostatic headset in the office, and I've not used it in over six months.