Cool!
Might you be able to please post the hardware you're using (phone make/model etc) and version of the Tidal app you're running?
I'm hoping the Tidal phone APK that supports Atmos is made available somewhere like apkmirror and that it could be sideloaded on the Shield ala the Xcloud app.
Agree completely that Atmos on the supported devices so far makes zero sense since that means stereo headphones but a device like the Shield that can bitstream makes all the sense in the world.
On the other hand if the app
doesn't support bitstream it will be useless.