disable-youtube-autoplay/disable-youtube-autoplay.user.js

// ==UserScript==
// @name         Turn off Youtube Autoplay
// @namespace    https://bubbletea.dev/
// @version      2.1.0
// @description  Disables Youtube recommended videos from automatically playing
// @author       shibao
// @include      https://www.youtube.com/watch*
// @downloadURL	 https://gitea.bubbletea.dev/shibao/disable-youtube-autoplay/raw/branch/stable/disable-youtube-autoplay.user.js
// @updateURL    https://gitea.bubbletea.dev/shibao/disable-youtube-autoplay/raw/branch/stable/disable-youtube-autoplay.user.js
// @grant        none
// ==/UserScript==

// from https://developer.mozilla.org/en-US/docs/Web/API/Node#recurse_through_child_nodes
function eachNode(rootNode, callback) {
  if (!callback) {
    const nodes = []
    eachNode(rootNode, function (node) {
      nodes.push(node)
    })
    return nodes
  }

  if (false === callback(rootNode)) {
    return false
  }

  if (rootNode.hasChildNodes()) {
    const nodes = rootNode.childNodes
    for (let i = 0, l = nodes.length; i < l; ++i) {
      if (false === eachNode(nodes[i], callback)) {
        return
      }
    }
  }
}

(function () {
  'use strict';

  const observer = new MutationObserver(function (mutationList) {
    for (const mutation of mutationList) {
      for (const addedNode of mutation.addedNodes) {
        // recurses through all child nodes as well
        eachNode(addedNode, function (node) {
          node.nodeName == 'DIV' &&
            node.classList.contains('ytp-autonav-toggle-button') &&
            node.getAttribute('aria-checked') == "true" &&
            node.click();
        });
      }
    };
  });

  observer.observe(document, {
    childList: true,
    subtree: true,
    attributes: true
  });
})();