[1] https://news.ycombinator.com/item?id=44734639
e.g. client requests https://github.mx/llvm/llvm-project, your server fetches the data from https://github.com/llvm/llvm-project (using an API or scraping the site), and renders it in a cleaner UI with less HTML and JavaScript.
It would be useful for slow/outdated devices and places with low internet bandwidth. The URL concept is similar to https://github.dev/llvm/llvm-project, which opens the project in a web-hosted VSCode (vaguely the opposite since VSCode is more UI but also more features).