Someone else already gave me a less condescending answer: Asking Siri to stop listening.Sure, disconnect the cable that goes to the wall.
Or, you know, don't buy a smart speaker if you don't want it to have a microphone. That's kind of their thing.
You know, there are many customers that actually want an AirPlay 2 enabled speakers but don’t like having microphones listening all the time. But if I find third party speakers compatible with AirPlay 2 that could be my answer.