The switch should pass Dolby Atmos via HDMI, the optical output cannot do that, whether the SONOS can handle the HDMI signal I cannot say.
From my personal experience with Dolby Atmos and the cabling of TV, amplifier, playback devices, etc., I can only say that the bigger problem is probably the playback device. Not every device that is capable of 4K/UHD and Dolby Digital+/Atmos plays the Atmos signal or outputs the signal.
My BluRay player, for example, passes on Dolby Atmos or DTS:X to the amplifier when playing a corresponding disc (the sound is brilliant, that's just by the way), the Netflix app integrated on the player can probably play 4K/UHD and also Dolby Digital+, but Dolby Atmos is not possible.
It depends very much on how up-to-date the software on your media player / TV is, whether Dolby Atmos works or not, sometimes you can't do anything because the software is no longer maintained by the manufacturer and therefore new functions are not integrated.
BluRay or UHD discs should not be a problem, except perhaps with older players, provided the settings in the player are correct.
At the end of the day, in my opinion, there are still very few films available in Dolby Atmos via streaming platforms, with discs it is a little better but mostly only in the original language, Dolby Atmos in German is very rarely available.