Hello Everyone, 

First time commenting on the board. Wanted to share what I’ve experienced with my Sonos Arc connected via ARC to a late 2018 Samsung QLED tv. All Dolby Atmos sound was via ARC/Dolby Digital Plus. I tested the following devices to see which had the best Dolby Atmos experience the past month. 
 

Roku Ultra and Roku 4K+ were the best for my set up because it worked with the most streaming services. 

1. Received atmos sound on Roku Ultra and Roku 4K+ stick. Note, the Roku 4K+ stick marketing language isn’t clear about it receiving atmos but both devices do based on my experience with Netflix, Apple TV+, HBO Max, Hulu, Disney Plus and Amazon Prime. Oddly, it appears that Roku’s overall marketing says Ultra is the only one that gets Atmos, but that’s not my experience. 
2. Received atmos sound on Amazon Firestick 4k on less streaming apps/services than the Roku. I don’t remember exactly which - but I believe it didn’t work on Netflix. 
3. No Dolby Atmos on Apple TV 4K (2021). The Apple website indicated that E-ARC was needed if a direct connection from Apple TV to the television was to be made. This seemed to be the case with my experience. I only have a ARC connection. 
4. No Dolby Atmos with any of my Internal built in apps of my Samsung QLED tv which included Disney. Prime. Netflix. HBO Max. Hulu. 

Hope that helps!