Connecting WiiM to Sonos One

Do you mean in a group?  If so no.  The WiiM can group with Amazon Echo speakers & Google Nest speakers, but not with Sonos.  At least not that I am aware of.

Yes you can group WiiM and Sonos devices via AirPlay.   

You are correct.  I never use AirPlay so was not aware.  My attempts were to create a group in the Alexa app using Echo, WiiM & Sonos.  Sonos does not cooperate in that scenario.

I have 2 Sonos players (an Amp and Port) that support AirPlay but will not ever work with AirPlay. Going through the troubleshooting doesn’t help. I’ll replace them with Wiiim units eventually, life’s too short to deal with stuff that doesn’t work. 

Before spending money, I’d certainly want to try Sonos Support first, although you may have, already. Certainly AirPlay 2 works in my system, so I’m wondering if there is something in your local networking that’s blocking it, be it Sonos or otherwise. The only cost for support is time and aggravation, but I’ve found that to be cheaper for me than spending money out of my wallet.