I posted this on a separate thread last month(?), where I looked at the Apple Music and Amazon Music functionality for the two versions of each service, and accessibility of the Atmos/Spatial tracks:
The native app (red icon with Apple symbol) on the DMP-A6 is limited to 44.1kHz. The interface is developed for the horizontal screen layout, and A6 native "now playing" screen has the full-screen options for album art, song / artist / album name, track progress. For spatial/Atmos tracks, I don't know if they are accessible, or if they auto-play instead of the standard track. There are no settings for streaming quality that I can find (opening the app provides a warning that it's limited to 44.1kHz), and no Spatial/Atmos auto-play setting, and no apparent way to toggle within a track's "now playing."
The downloadable app (music note symbol on red background) supports the hi-res/lossless tracks if you have the settings set to enable the higher resolution files enabled. The interface on the A6 screen looks like a desktop app with small icons to tap. Music playing will appear on the right hand side of the screen in a "now playing" pop-up (similar to what comes up full-screen on mobile phones), and you won't be able to get full-screen "now playing" info. For spatial/Atmos tracks, I don't know if they are accessible or if they play in place of standard tracks. There are settings for streaming quality, but no Spatial/Atmos auto-play setting that I could find, and no apparent way to toggle within a track's "now playing" track version. The interface is low-res, a bit blurry, and tapping on "About Lossless Audio" in the audio quality > wi-fi settings screen took me to a Google Chrome browser page. Note that in this Wi-Fi Streaming settings page, setting it to "Hi-Res Lossless" (ALAC up to 24/192) brings up an "external hardware suggested > to play content in Hi-Res Lossless at full resolution, you will need an external DAC" warning. That might be default because this app is ported from elsewhere, like iPad/Android browser interface? Because I was able to play a Hi-Res Lossless track (24b/192kHz ALAC) just fine.
You can control the music playing from the device's app on your phone, either within the app or via the app's "Cast" screen mirror function.
I think the only way to start the A6 is to press the power button on the unit itself (depress the volume dial). Otherwise the mobile app won't connect to the unit.
It supports AirPlay, of course not for full hi-res lossless tracks, but that I believe allows control from the iOS Apple Music ap. I don't use it this way, so I can't verify off the top of my head.