You can get very cheap digital to digital audio hardware that can convert any multi-channel audio stream (DRM or otherwise) to straight multi-channel PCM. I personally, occasionally, use an RME Babyface Pro (not cheap) for this purpose, but there are many options available. You can even do this purely in software. On Windows or Linux look at Jack. On MacOS I guarantee it's available.

As an aside, Atmos is generally lossy. It's actually a terrible format for music distribution. It's only popular due to marketing.

Interesting video from Benn Jordan at https://youtu.be/5Dw3aKbw5Wo