You misunderstood. “Official” can be interpreted in different ways. There’s “official” in the sense that the Caddy team maintains the https://apt.fury.io/caddy/ repo, but it’s “unofficial” in the sense that it doesn’t ship alongside debian.
You probably installed it correctly, but you have two
caddy things in your PATH. One from the package we provide, and one from some Python thing. If you do
which caddy, you should see
/usr/bin/caddy If you see something else, then it’s because something else is taking precedence over
caddy the web server. If you run
caddy version you should see something like this:
$ caddy version
It’s up to you to figure out what installed this other “caddy” thing. I’ve never heard of it.