Haven't used javaFX for a while but this is worth a shot
My son found a disk with some of my old java project from college 20 years ago and that's about what it took to run them, first figuring out how to even download java and then making some minor changes to get them running. I think we gave up trying to get the actual applet based ones to run.
You also need a browser that has NPAPI. IE 11 was the most modern browser I am aware of that still supported applets.
The old GUI framework mentioned in the GP might have been Swing. It is still included in most JDKs and allows for cross platform desktop GUI application development with no other dependencies outside the JDK. Finding documentation on how to do GUIs in Swing is getting increasingly difficult though.