book/scripts-greasemonkey/twitter_to_nitter.user.js

// ==UserScript==
// @name        Twitter to Nitter
// @author      Jesús E.
// @namespace   NitterRedirect
// @description Scan page for Twitter and urls replace with Nitter
// @homepageURL https://git.sr.ht/~heckyel/book/blob/master/scripts-greasemonkey
// @include     *
// @exclude     /^http(s|)://(www[.]|)nitter[.]net/.*$/
// @exclude     /^http(s|)://(www[.]|)nitter[.]pro/.*$/
// @exclude     /^http(s|)://(www[.]|)nitter[.]snopyta[.]org/.*$/
// @exclude     /^http(s|)://(www[.]|)nitter[.]42l[.]fr/.*$/
// @exclude     /^http(s|)://(www[.]|)nitter[.]13ad[.]de/.*$/
// @exclude     /^http(s|)://(www[.]|)nitter[.]nixnet[.]xyz/.*$/
// @exclude     /^http(s|)://(www[.]|)nitter[.]drycat[.]fr/.*$/
// @exclude     /^http(s|)://(www[.]|)tw[.]openalgeria[.]org/.*$/
// @version     0.1.4
// @grant       none
// @license     GPL version 3 or any later version::: https://www.gnu.org/licenses/gpl-3.0.html
// ==/UserScript==
/* jshint esversion: 6 */

// Set you favorite Nitter instance! (https://github.com/zedeus/nitter/wiki/Instances)
let instance = 'nitter.net';

// Console Style - Debug
const consoleCSS = 'background: #000; color: #00FF00; padding: 0px 7px; border: 1px solid #00FF00; line-height: 16px;';
const name = GM_info.script.name;
const version = GM_info.script.version;
const log = (...args) => console.log('%cUSERSCRIPT | %s %s | %s', consoleCSS, name, version, ...args);

// Do the actual rewrite
function rewriteLinks() {
  for (let i = 0; i < document.links.length; i++) {
    let elem = document.links[i];
    if (elem.href.match(/http(s|):\/\/(mobile[.]|www[.]|)twitter[.]com\/(#!\/)?(.*$)/i)) {
      elem.href='https://' + instance + '/' + RegExp.$4;
    }
  }
  log('successfully initialized');
}

window.addEventListener('load', () => {
  rewriteLinks();
});