if you visist kde.org and then neon.kde.org the browser downloads the stuff twice despite being the same files
The fonts need to be moved to cdn.kde.org. By the way, bootstrap and jquery are now hosted in the CDN and this need to be used between kde.org and neon.kde.org too (for the moment only userbase use it). https://cdn.kde.org/aether/css/bootstrap.min.css https://cdn.kde.org/aether/js/bootstrap.min.js https://cdn.kde.org/aether/js/popper.min.js https://cdn.kde.org/aether/js/jquery.min.js
Actually, it's impossible to not download the font twice. In recent years chrome and firefox started to not allow sharing assets between websites because of security reasons.