there's sadly no community solution AFAICT

Why cant an android phone with ethernet tethering to a router suffice?

I've done this using an android phone, usb-c hub w/ethernet nic, and and edgerouter lite before.

The biggest missing piece i see is the option for an external antenna.

I don't understand how that fixes the awful Sonos software.

Whoops, I replied to the wrong subcomment.

The antenna is often more important than the receiver