Hides the app-drawer aka guide menu by default

hide-youtube-guide.user.js

// ==UserScript==
// @name        Hide youtube guide menu
// @namespace   Violentmonkey Scripts
// @match       https://www.youtube.com/*
// @grant       none
// @version     1.0
// @author      -
// @description Hides the app-drawer aka guide menu by default
// ==/UserScript==

function hideGuide() {
  'use strict';
  const appDrawer = document.querySelector('tp-yt-app-drawer#guide');
  if (window.location.pathname !== '/watch' && appDrawer !== null && appDrawer.hasAttribute('opened')) {
    appDrawer.removeAttribute('opened');
  }
}
hideGuide();
window.addEventListener('yt-navigate-finish', hideGuide);

I think in the if condition, we should check for appDawer is not null, before accessing hasAttribute, to avoid null pointer exception, e.g.

if (window.location.pathname !== '/watch' && appDrawer !== null && appDrawer.hasAttribute('opened'))

When used together with Tree Style Tab add-on for Firefox and "YouTube Video Preview and Ratings Keyless" script, going to fullscreen (during video preview) and back restores big guide menu on the left of channel page (in Home, Videos, Playlist tabs).