I occasionally check my LG C1 Apple Music app to see if Dolby Atmos support was added while I was off playing with other streamers. Checking it tonight, I noticed Dolby Atmos is now supported, though it must be cranked up like the Tidal app to get it loud.
LG ThinQ iOS app:
LG C1 TV webOS Apple Music app:
The LG C1 bitstreams the signal and “Dolby Atmos/DD+” is displayed as the incoming signal.
Onkyo Controller iOS app:
The Apple TV 4K uses Dolby MAT2.0 to decode and output the signal as LPCM while retaining Atmos metadata. This results in an input signal display of “Dolby Atmos” on my Onkyo. My Yamaha would display “Dolby Atmos/PCM.”
Onkyo Controller iOS app: