Posted on the firecore forums from a user:
"For what it's worth, utilizing tvOS 12 beta 2 and Infuse Pro, my receiver does indicate Dolby Atmos when watching a TrueHD 7.1/Atmos movie. When playing the same movie on Plex using the nvidia Shield, it indicates Dolby Atmos-TrueHD 7.1. I'm not sure why it displays differently or if it means anything...
In Infuse, when setting audio output to "Passthrough", I get no audio, though when it is set to "Auto" I do get audio indicating Atmos - the audio has a delay when starting (several seconds after the video starts), but is in synch. Hope this info helps someone."
Streaming Devices: Nvidia Shield, 2x Roku 3's, 1st/2nd gen chromecast, ATV4k, Apple TV 4, xbox 360/one
Displays: Vizio M602i-B3, LG OLED65B6, panasonic ax100u on a 145" S-I-L-V-E-R painted screen, 40" Samsung
Receivers: Denon X3300, Yamaha RX-V663. Bluray/UHD player: Oppo UDP-203