Enable Push to Talk

[rahulsom]

Google Meet now supports a Push-To-Talk mode where hitting space can unmute you.

[chrisspiegl]

Not directly related to Google Meet; but you could use the Audio Mute plugin for the Stream Deck to achieve this on a system input level:

https://marketplace.elgato.com/product/audio-mute-705c5433-1e05-4d8a-844f-b5914b7f642f

It can toggle mute, but it can also be used to Press to Unmute / Press to Mute modes.

Maybe that solves your issue.