code:

// ==UserScript==
// @name         x.com -> twitter.com
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Fix twitter links on SA threads
// @author       WrasslorMonkey
// @match        https://forums.somethingawful.com/showthread.php?*
// @match        https://forums.somethingawful.com/newreply.php*
// @match        https://forums.somethingawful.com/editpost.php*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=somethingawful.com
// @grant        none
// @run-at       document-start
// ==/UserScript==

(function() {
    'use strict';

    // Add domains to replace with 'twitter.com'
    const domainsToFix = [
        'nitter.net',
        'www.twitter.com',
        'x.com',
    ];

    // Create selector to find bad links
    let selectors = [];
    domainsToFix.forEach((domain) => {
        selectors.push(`a[href^="https://${domain}"]`);
    });
    const selector = selectors.join(', ');

    // Replace links
    function checkLinks() {
        const as = document.querySelectorAll(selector);
        [].forEach.call(as, function(a) {
            domainsToFix.forEach((domain) => {
                a.href = a.href.replace(`//${domain}`, '//twitter.com');
            });
        });
    }

    // Set up an observer so we don't run this more or less than needed
    const targetNode = document;
    const config = { attributes: false, childList: true, subtree: true };
    const observer = new MutationObserver(checkLinks);
    observer.observe(targetNode, config);

    // First try, I assume this will do nothing since we are running at document start
    checkLinks();
})();