Bleh. Not easily, most often a 3.5 mm headphone jack is a stereo output, not what you want to feed to a Sonos soundbar capable of much more. 

I’d probably extract the sound before it reaches the projector, using an HDMI switch that creates an eARC signal to send to the Arc Ultra. 

There is the HD Fury Arcana, the Feintech VAX04101k, and the OREI HDA-935. You can also order from those links from the companies directly, or check your local retailers for availability. Amazon may carry some, depending on location. At this point, there may be more manufacturers, I haven’t been keeping track.

Thank you for your information