The quickest way is to open the ‘Now Playing’ screen for the Home Theatre room in the Sonos App and look for the label showing the ‘Audio In’… see attached screenshot and section circled in red for the current audio format playing in the room. 

Hii. The app will tell you if it's Dolby Atmos in the same places that it is currently telling you it's PCM etc.

Thor on Disney+ is in Atmos.

Does your TV definitely support Atmos? How old is the TV and what is the model  number?

A film to perhaps try is ‘6 Underground’ on the Netflix App - requires a premium subscription plan, or maybe try Jack Ryan (season 2) on Amazon Prime Movies.

If The Sonos app does not say you are getting Atmos, you could check if your TV (and/or the apps on it) are Atmos capable. Most older are not, and on newer TV's some apps are not.

“Mudbound” on Netflix is very good mixed in Dolby Atmos. Not only for the Atmos effects, it a great movie overall. When you start that movie, you will immediately hear the rain coming from the ceiling.

To get Atmos on Netflix you need to have a subscription to the UltraHD tier.

This is great, thanks so much for your help!

MY TV is an LG 43UM7500PLA UHD 4K HDR, bought it in 2020.

I just presumed it would be good enough for Atmos if it had the HDMI ARC connector. I’ll do a bit of research now.

Thanks for the film recommendations! 

Hi, I think to get Dolby Atmos from the Gen 2 Beam you need a TV that has eARC, looking at the specs of your TV it looks like its just ARC.

I’m in the same boat, got a LG TV a couple of years back and its only ARC, so no Beam upgrade for me yet.

Not completely true. Atmos can be streamed in a DD+ stream. Most apps on TV's use such a compressed stream.

BD-players or Apple TV's etc are also capable of sending uncompressed Atmos. To pass those through the TV you neeed eARC. 

Yes, this is what I understood to be the case. HDMI ARC should be fine with Atmos.