You can get rid of the JS by setting the autofocus[1] attribute to the textarea.

[1] https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...

Thanks, I trimmed it down to this:

  data:text/html,<title>Notepad</title><textarea autofocus spellcheck=0 style="position:fixed;inset:0;padding:1em;border:0;font:monospace">

Thank you, I'm going to try this.