Are there common patterns or examples of directives that operators should be aware of?

I know the post linked to systemd docs, but I’d enjoy seeing some snippets of directives people are using to achieve this kind of hardening.

There seems to be some formatting issues on the current version of the site.

The GH page is easier to read: https://github.com/zelang-dev/c-asio

Does anyone have an idea of how this is built? I wonder if they are using QUIC with relay servers or something like Tailscale's DERP.