Our main docs are built with Hugo (https://github.com/mitmproxy/mitmproxy/tree/main/docs). For our API docs we use pdoc (https://pdoc.dev), which integrates well with most static site generators. pdoc is also maintained by us. :)

Thanks. When you began working on the main docs, did you start with a pre-built theme or did you start from scratch?

If I'm not mistaken they are built from scratch, but that part wasn't built by me. IMO the by far hardest part is actually writing the docs. :)