TextReplace.js

// ==UserScript==
// @name         TextReplace
// @namespace    https://guarandoo.jp
// @version      0.1
// @description  Simple text replacement
// @author       [email protected]
// @match        https://www.lowendtalk.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    const replacements = [
        {pattern: new RegExp("EASTER 2021"), replace: 'XXX'},
        {pattern: new RegExp("LowEndTalk"), replace: 'YYY'},
    ];

    let walker = document.createTreeWalker(
        document.body,
        NodeFilter.SHOW_TEXT,
        {
            acceptNode: node => {
                if(node.nodeValue.trim()) return NodeFilter.FILTER_ACCEPT;
                return NodeFilter.FILTER_SKIP;
            },
        },
    );

    let node = null;
    while(node = walker.nextNode()) {
        let value = node.nodeValue;
        replacements.forEach(repl => value = value.replace(repl.pattern, repl.replace));
        node.nodeValue = value;
    }
})();