I’m not sure I understand your request. The Sonos Arc already supports eARC. I use the HD Fury Arcana device between my sources and my Vizio TV, which does not support eARC, in order to get an Atmos signal to the Arc. 

The HDFury Arcana is a solution for the lack of eARC on a TV (or in your case projector), not on the Sonos Arc.  As Bruce says, the Sonos Arc is already eARC compatible.

Thanks Bruce and John , I got it

I have the same question.  The $800 Sonos ARC is already expensive.  The product supports HDMI ARC/eARC, but not audio from standard HDMI content sources.  The difference is that ARC/eARC uses a different set of pins and may decoding the signal differently.  Projectors are just beginning to support ARC, and it is common for them to simply send a stereo signal back on the ARC channel.  As a result, it was impossible to get ATMOS content to a Sonos ARC until the release of the $200 HDFury device, which extracts the ATMOS and surround audio and sends it on a seperate HDMI channel on the ARC pins.  For projector users and anyone with a TV that isn’t quite new, getting surround really requires $1000, not just the $800 for the soundbar.

If Sonos ARC support standard HDMI audio channel AND ARC/eARC, the $200 purchase would not be necessary.  Or, perhaps, an inexpensive HDMI splitter would suffice. 

Question:  Will Sonos add support for standard HDMI audio, and if so, when? 

For more, this article explains the problem:  https://www.trustedreviews.com/reviews/hdfury-arcana

Like the original author, I would like Sonos to make the update, and I am postponing my ARC purchase due to this problem.