OrdinaryJellyfish one problem with that is that while Flarum is a Single Page App, it does not mean the front-end pages are static. Flarum pages are dynamically created with the data needed to bootstrap the app, so you can't cache those. You could maybe cache some of the pages for guest users, but it needs to be refreshed regularely if you want for example the latest discussions to be shown when the homepage is displayed.
What you could already do to improve performance is move the assets
folder. This will probably require a few changes for Flarum to write to the CDN instead of your local filesystem, as well as update the urls to point to the external assets host.