This is a quick reference note, and not a question.
If anyone ever has a client specification which requires progressive enhancement, or the need to have at least a page available as HTML only to direct non JS users to offline or alternative services, you can do this easily.
In your native libraries, add your html only content between noscript tags:
<noscript>
<p>If you have JavaScript disabled you will not be able to use this application properly. For our offline service please email........<p>
</noscript>
If you invest a little bit of time to strip them down, you can actually make any of your own or Anvil’s page templates work this way.
If you want to test this, just turn off JS Enabled in your browser and take a look at the published url of your app before and after. Works a treat.
Anyway, hope this helps someone else in future.