@FrenchJu
No, it isn’t possible to get surround sound via Airplay on Sonos. And directly via Sonos you will need one of the Sonps home theater device to create such a setup.
Damn, such a shame…
Is there another way ? Like plugging AppleTV to a Sonos Amp, and then use 4 Sonos SL as surround system ?
Apple only sends a stereo signal to any non-Apple devices via AirPlay 2.
However, I ‘think’ that Apple changes the ‘originating device’ when you AirPlay 2 to an Apple TV from another Apple device, so you could indeed use an Apple TV as a source, but then you’d need a Sonos surround sound capable device connected to your TV. You wouldn’t be able to use four Sonos Ones, though. You could use a Sonos Amp, driving a front pair of non Sonos speakers, and add the pair of your Sonos Ones as surrounds, or go with a Sonos soundbar (the Ray, Beam, or Arc) as the front speakers, and add your current Ones as surrounds again.