Plus one-ing this - I think the external monitor may be the kicker to keeping the mic active. This drives me up the wall when Google Meet decides to just default to the closed Macbook next to me instead of my already connected Air Pods when joining work meetings.

Are you sure it’s the MacBook (T2 or Arm) mic? I imagine you’d sound super muffled if you were trying to use it while closed anyway, so I can’t imagine it’s very usable to yourself?