I'm not an AT Proto wizard (there's a lot of good text and video explainers out there) and I know that Tangled is building on it but also adding their own functionality. But from a high level, I register my 'knot' with my account on Tangled.org which is exposed through a public domain. In my case that's routed through a Cloudflare tunnel to a reverse proxy running on my server. Tangled is then running an "app view", which is basically an aggregate of a subset of AT proto activity. So my commits, PRs, releases, etc go into the app view which then points traffic back to my server. So the long and short of it is the app view is the missing piece of the AT proto system and you have to register your data with an app view provider, of which Bluesky is the most prominent. But there are open source app views, in fact the Tangled team just announced one called bobbin that's super resource light.
Additionally (and optionally for Tangled use), I'm also hosting my own PDS which is my personal data server. This is the home for my AT proto profile, which contains all of my AT proto activity like Bluesky comments and likes. Tangled does look at the PDS for identity but the code is in the parallel structure of the knot. I suspect this is cause AT proto wasn't built for code so the PDS isn't sufficient for an entire git repository but don't quote me on that.
Finally I'm running a spindle, which is just a CI runner, and that's registered with Tangled very similarly to how a self-hosted GitHub or Gitlab action runner would be.