Use bluetooth microphone in Google Assistant
I had the same problem with Google Voice Access. I came across these instructions, which seem to be for Google Assistant. Executing them did not seem to affect the desired change in Voice Access, but I think they might work for you with Assistant.
The configuration is performed in the main Google app. After opening it, I clicked &quot;⋯ More&quot;, then &quot;⚙ Settings&quot;, then &quot; Voice&quot;, and there - under the &quot;Hands-Free&quot; heading, I found an option for &quot;Bluetooth audio recording&quot;, subtitled &quot;Enable audio recording through Bluetooth devices if available. See the linked instructions for screenshots.