Thank you for the replies @vader, @joepirello and @smapmap.
Like @mads and @Eeems, I don't know how to remap the button.
And I don't know how to delete the Google Assistant cache. In Settings > Apps, Google Assistant is not listed at all. I deleted the Gemini Voice Assistant cache, but still nothing.
Can anyone give more info how how to remap the button please?
@vader also it made me register my voice, but I have to wake it and enter my password before it will respond to my voice, so I can't talk to it to get it to do anything when it's in sleep mode!