The getting started CDN example is currently broken. The links to version 2.2.0 return a 404 and is missing a link to download material icons. Here's what I used to get it working:
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@materializecss/[email protected]/dist/css/materialize.min.css">
<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/@materializecss/[email protected]/dist/js/materialize.min.js"></script>