Hard to find but this is available:

Thanks, Stanley, I have already done that, which at least enabled Sonos to recognize the folder, but Sonos shows no content. I also enabled DLNA streaming, but no luck. I'm running Windows 11 on a fairly new Lenovo Yoga.

For the record, neither my smart TV (LG) nor my Roku recognize it, either. So while I agree with another poster that Sonos is not remotely user friendly, there must be something on the Windows or network side causing the problem.

Also for the record, I have no trouble casting the laptop directly to the TV, so I guess that's my solution for now, unless someone else has discovered the secret. 

I gave up on Windows and used a Raspberry Pi (Samba / SMB) to serve up my music, don't think I've touched in many months now, it just works.