My Current HTML Boilerplate
I've never thought to do something like this as a way to detect whether or not js is being used.<p><pre><code>    <html lang="en" class="no-js">

    ...

    <script type="module">
      document.documentElement.classList.remove('no-js');
      document.documentElement.classList.add('js');
    </script>
</code></pre>
It's so simple but so effective. Will be copying that.