Yes, exactly!

Edit: ...actually, almost! You don't even need Traefik, but this actually doesn't handle ports for you. You'll still need to visit sonarr.local:port. If you want to get rid of the ports, you'll need to set up Traefik or another reverse proxy - see the compose_example.yaml in the repo for a simple example.

If your containers are already available at server_ip:port, on your local network, whether directly or by another proxy, you can just add the label (traefik.http.routers.x.rule=Host(`example.local`)) to the container and this will pick it up, no Traefik needed. (And then visit example.local, or example.local:port if not 80.)

I'm meaning to rework the README a bit to make this clear, and perhaps add a simpler label you can use :)

Edit 2: Reworked the README a bit and added support for a quack_domains.hosts label so you don't have to write out all that Traefik stuff if you don't want :) But to access multiple services without a port, you'll still need to set up a reverse proxy like Traefik, or nginx, or Caddy.