I was recently trying to figure out whether the microphone is usable when using my notebook in clamshell-mode. Turns out Apple added a privacy/safety feature to all Apple silicon-based Mac notebooks and Intel-based Mac notebooks with the Apple T2 Security Chip. It will hardware disconnect the microphone when the lid is closed, based on the lid sensors.
Pretty cool safety feature!! Even though I'm sad I can't use my mic in clamshell mode
Pretty cool safety feature!! Even though I'm sad I can't use my mic in clamshell mode