Tampermonkey script to add PTT to google meet.

spacebar-ptt.user.js

// ==UserScript==
// @name         Google Meet Spacebar PTT
// @namespace    https://github.com/mikerawding
// @version      0.1
// @description  Use Spacebar as Push-To-Talk for Google Meet
// @author       Mike Rawding
// @match        https://meet.google.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
const hotKey = 'Space'
let hotKeyDown = false

const toggleMute = () => {
    document.dispatchEvent(
        new KeyboardEvent("keydown", {
            key: "d",
            keyCode: 68,
            code: "KeyD",
            which: 68,
            ctrlKey: true,
        })
    )
}

window.addEventListener('keydown', event => {
    if (event.code === hotKey && document.querySelector('[data-is-muted="true"]') && !hotKeyDown) {
        hotKeyDown = true
        toggleMute()
    }
})

window.addEventListener('keyup', event => {
    if (event.code === hotKey && document.querySelector('[data-is-muted="false"]')) {
        hotKeyDown = false
        toggleMute()
    }
})
})();

Done, thanks.