I’ve had this issue for over a year with my One SL.
I recently added a Sonos Roam to my Sonos system and would like to try one more time for a solution.
I started with a One SL (for the airplay 2 support, mainly) in hopes to send audio from my Apple TV to my Sonos and Vizio soundbar (connected directly to tv via optical audio) as a group. Along with reports from the rest of the sonos community using airplay, the sound is never synced.
Maybe 1/50 times, the sound somehow syncs but that is extremely rare.
I gave up on this months ago, but have just added a Sonos Roam to my setup and was hoping this issue had been fixed through some kind of software update, but it has not.
I read that disabling the wifi on the One SL and using Ethernet, pairing the 2 Sonos speakers together via the sonos app rather than adding these speakers separately via airplay on the Apple TV, and changing with the audio output on my tv might resolve the sync issues. But, it. Did. Not.
It would be nice to have some kind of audio delay settings with the One SL instead of having to purchase a much more expensive system that enables this setting.
Curious to see if anyone else has found a solution..