Let's say, for example, I feel like hosting my game on another site, that only accepts uploads as .zip files, containing an index.html file, etc. Is it possible at all to export my game as a HTML5 archive? I remember reading somewhere that Quest is for making HTML5 games, so it seems logical that it should be able to.

The frontend of a Quest game is HTML and JS. The backend is a server-side application; so Quest needs to be installed on the server.

Quest 6 games can be exported as an HTML archive; but that's a completely new system.

6 is built with this functionality in mind, but it's a different system, yeah. It's currently working, but the GUI editor is a work in progress, and converting between 5 and 6 is also WIP and may never be 100% perfect.

Well, if I haven't really started my project yet, surely switching to 6 would be easier.

...Plus, I'd need to know where to get Quest 6.