Since the latest Nvidia Shield OS update to Android 11, Plex Atmos support is inconsistent. Some movies play in TrueHD Atmos, others play in 2.0, and others in TrueHD 7.1 (all according to the Sonos app). PlexDash says nothing is being transcoded and it’s all direct play.
Atmos playback does work in other apps on the shield with the same files. Appreciate the help!