Agreed but where is the actual git repo? I see a text saying this "contents get updated automatically on every commit to this git repository" but where is "this git repository"?

I can't find a link to the source anywhere.

The introduction has a "help out" section which links to the github repo: https://github.com/bagder/http3-explained

After a quick google: https://github.com/bagder/http3-explained

(using a search engine is faster than asking for a link on HN)

I found it on HN faster than I could have with a search engine because they asked :)