I'm having the same issues and doubts like everybody else. I have a Denon Atmos capable received but I was never able to see any Dolby symbol in the display resembling Atmos so I was not sure if my receiver was even able to decode Dolby Atmos until today. I heard from good sources there are already titles on Apple TV 4K running IOS 12 that can be played in Dolby Atmos such as Jumaji and Blade Runner 2049 among others but did not want to rent or buy anything until I was sure my received could decode Atmos. This is what I did:
1) I downloaded the compatible DD+ Atmos file sample directly from Dolby site: https://www.dolby.com/us/en/guide/test-tones.html
2) I added the downloaded sample to my iTunes
3) Go iTunes preference and share your iTunes library
4) Go to your Apple TV and click on the COMPUTERS app
5) Select your library
6) Click on Home Videos
7) Play the Atmos Sample
If you have a Atmos compatible receiver then you will see the Atmos logo on receiver display.
Seeing the Dolby Atmos logo was amazing. it lifted a have load from my back. lol
1) I downloaded the compatible DD+ Atmos file sample directly from Dolby site: https://www.dolby.com/us/en/guide/test-tones.html
2) I added the downloaded sample to my iTunes
3) Go iTunes preference and share your iTunes library
4) Go to your Apple TV and click on the COMPUTERS app
5) Select your library
6) Click on Home Videos
7) Play the Atmos Sample
If you have a Atmos compatible receiver then you will see the Atmos logo on receiver display.
Seeing the Dolby Atmos logo was amazing. it lifted a have load from my back. lol