autochange_google_meet_account.js

// ==UserScript==
// @name         Google meet change account
// @namespace    https://gmelikov.com/
// @version      0.1
// @description  Autochange google account, if not defined
// @author       Gmelikov
// @match        https://meet.google.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var DEFAULT_USER_NUMBER = 2; // SET YOUR USER NUMBER HERE!

    var current_location = window.location;

    var url = new URL(current_location);
    if (url.searchParams.get('authuser') == null) {
        url.searchParams.set('authuser', DEFAULT_USER_NUMBER);
        window.location.replace(url.toString());
    }
})();