How are you currently watching Apple TV+? What model TV do you have? Do you have any external media devices connected to the TV?

Thanks for your reply.

Watching TV on a two year old LG OLED65CXPUA via Spectrum cable in SoCal.  I do indeed have an Apple TV device BUT, am currently watching Apple TV+ via the Spectrum cable box via MDMI 2.1 as Apple TV+ is convenient and listed as an available Spectrum stream source. Other members of my family are hesitant to select another TV input source, other than Spectrum, so I am trying to simplify their lives.  I understand that one must go through the Sonos app to get spatial Apple Music and wondered if there was such a proviso for getting Dolby Atmos TV sound via Apple TV+.  I am willing to go back to my Apple TV device if that would simplify matters regarding the Dolby Atmos experience.

Set the TV to these settings:

HDMI Input Audio Format: Bitstream

Digital Sound Output: Pass Through

eARC Support: On

Then try downloading the Apple TV+ app on your TV and test the film Finch. Check the Now Playing screen in the Sonos app to confirm that it is playing in Dolby Atmos.

And if you download the TIDAL app on the TV, you should be able to play music in Dolby Atmos. But this does require a subscription. They probably offer a free trial. Test the song “King Ghost” by Steven Wilson.

If you have an Apple TV 4K, you can stream Dolby Atmos from all the major streaming apps including Apple TV+. You can also stream music in Dolby Atmos from Apple Music and TIDAL. In the Apple TV settings under Audio Format, set Change Format to OFF. And go to Apps > Music and set Dolby Atmos to Automatic.

Wow!  Success!  Thank you!

I was able to get the Dolby Atmos indication to appear under Living Room (my Sonos Surround location) for Apple TV+ via Spectrum AND via the TIDAL app (did the free trial for HiFi plus) for music stream.  Oh, and the sound was great!

I will connect my Apple TV device next week when I redo some wiring connections and try things noted in your third paragraph above.

As to my LG TV, the HDMI Input Audio Format choice field persistently remained grayed out, BUT, I got the Atmos indication on the Sonos app, so maybe it defaulted to Bitstream when I chose eARC, or something, in another field. Sound was immersive.

A side note:  I saw the movie Oppenheimer yesterday and then watching Finch was a bit grim for me. This nuke stuff can wreck your whole day.

Anyway, thank you for being there for us Sonos Explorers.  I learned a lot with your help.

Glad you got it working.

The HDMI Input Audio Format setting only applies when connecting an external media device to the TV via HDMI. So this setting will be active when you connect the Apple TV 4K.

A pleasant surprise for me as the Netflix series, Lincoln Lawyer resumed. It was in Dolby Atmos and sounded great via Netflix via Spectrum Cable.  Thanks again.