Yes, Flavour apps are an index.html file and a classes.js file (plus optional CSS, images, etc. as desired). So with as few as 2 static files you can serve up a Java-based modern web app in a web browser.

For example, try Wordii, a 5-letter word game here: https://frequal.com/wordii/

If you look in the network tab, you can see it is loaded as a small HTML page, a classes.js file, and a few CSS files. All of those are served as simple static resources.

More information on how Wordii was created: https://frequal.com/java/MakingWordiiAPureJavaSpa.html