I have the exact tv, and will be getting my arc today so I will let you know. My theory is that It will work fine with dolby atmos when you have the appropriate setting in the audio section for the apple tv. But then when it comes to everything else it will play in stereo unless you change it back to 5.1.

Will be frustrating at first, but I believe a fix will be implemented within the next few months for the proper support on the arc.

I have a Sony X900F.  The X900F is connected to a Marantz receiver through ARC.  On that setup I get Dolby Atmos when watching native TV apps, so that means my TV is outputting DD+ (per the spec).  I would imagine the same functionality for the Sonos ARC.  Since my other sources are connected direct to the receiver, I don’t know if the TV will “pass through” DD+ over ARC, but honestly I don’t see why it wouldn’t.  

There are multiple reports that this TV is not delivering DD+ or Atmos to the Sonos Arc for whatever reason. I am very interested if you find this is not the case if you get an Arc. I know there are posts out there that state the x900f passes DD+, but so far no one reports that’s the case with the new Sonos arc plugged in. 

I'll be following this topic then. I have an A8F in my living room connected to a playbar. If I get an ARC it will be to upgrade that. However I probably won't if DD+ won't pass through. 

@peterbault 

Your question is really a Sony issue (or that of any TV manufacturer) and not Sonos. Below is the official word from Sonos regarding audio reproduction by the Arc for any TV:

Sonos Arc can connect to TVs with eARC, ARC, or optical outputs. For greatest compatibility, eARC is recommended.

If you connect to a TV with eARC, the Dolby audio formats supported include Dolby Atmos, TrueHD, MAT, Dolby Digital Plus, and Dolby Digital.

If you connect to a TV using ARC, the Dolby audio formats supported are dependent on your TV model and manufacturer. The TV may be capable of sending Dolby Atmos, Dolby Digital Plus, and Dolby Digital. An ARC connection cannot support TrueHD or MAT.

If you connect to a TV using the optical adapter, the Dolby audio formats supported are dependent on your TV model and manufacturer. The TV may be capable of sending Dolby Digital. An optical connection cannot support Dolby Atmos, TrueHD, MAT, or Dolby Digital Plus.

Glad I found this thread as I’ve been trying to figure this out for days. I have the Sony x900f connected via ARC to the new Sonos ARC. I’m getting an ATMOs signal from the Sony TVs built in Netflix app but not the Apple TV. I’m hoping I’m missing a setting in the Sony for pass through but I can’t find one. From what I’ve read in forums it should be able to pass through the Apple TV signal to the TV. If anyone else has got ATMOs working with the x900f and an Apple TV or other external streaming device please share how you did it. 

Ok I am super confused. I have Sony 900f, the  arc isais via high speed HDMI cable to HDMI input 3.  But Netflix still only shows Dolby digital 5.1 under " about my system " . It's driving me nuts. What am I doing wrong?. I went to Sony TV options as well and set it to Dolby digital plus.  Disney plus shows 5.1 digital plus only. But least it shows digital plus .  

I believe the Apple TV is not making the “handshake” with your TV if it is NOT advertised as an ATMOS TV. I have a Sonos ARC on order and a Sony X900E with an Apple 4K TV. I think the native app is the only way this may work. https://support.apple.com/en-us/HT204069

I own a Sony 75x850f and I also could get Atmos from my TVs Netflix app but nothing else. Apple TV 4K was a no go for Atmos for me so I switched to a Nvidia shield tv ( the newest cylinder shaped one) and haven’t looked back! I now get Atmos on all apps that support it. Hope that helps you.

I don't have apple tv. I am saying native internal tv on 900f netflix app does not show atmos. I see the icon for it on Netflix. But when I click play and then go to "about my system" it says Dolby digital 5.1 

Everything I’ve read about how Netflix works is that if it shows 4K or HDR when you click on a show, then your device is compatible and that’s why it shows. On my non 4K tv, all 4K content on Netflix shows HD in the description. On my 4K TVs and HDR TVs, it will show 4K and HDR for content that supports it on the devices that support it. Not sure why about my system section shows 5.1 and not atmos for example. This is at least my experience, but I could be wrong regarding the audio part.

Issue solved !  I had to simply restart the tv.