I have three Echo dots connected to Sonos either through line-in jacks or Connects. This was originally done to work around the Audible issue. The bonus of doing this was that all output from the Dots sounded great going through the Sonos speakers. Even, simple things like: "Alexa, what is the weather?" sound very good. Well, they don't with ducking, because you can't hear them at all now.
Perhaps the long-term fix is to assign Alexa devices to specific Sonos products. A short-term fix would be to add the option of turning ducking off. I would be willing to accept that Alexa might not be able to hear me with this option.
Best answer by Keith N
I will be sure to update this thread with any new information as it becomes available.