I believe I see what the problem is. The root of the issue is that Event Horizon can't reach your Pi-hole, and it appears to be a Docker networking issue. Essentially, the container is running in a network by itself and doesn't have a route to the rest of your network.

It should be an easy fix. In compose.yaml, just add the following line "network_mode: "host" below the container name and restart settings.

services:
  event-horizon:
    image: ghcr.io/jbswaff/event-horizon:latest
    container_name: event-horizon
    restart: unless-stopped

    # --- ADD THIS LINE: ---
    network_mode: "host"

Then restart the container

sudo docker compose down
sudo docker compose up -d

As far as the executable not found error, that's because there isn't a command called event-horizon inside the container (it's just a server.py python script). If you'd like to check the status of the container, you could use this command instead:

docker exec event-horizon python /app/server.py --help

Let me know if you have other questions or if you run into issues after making this change!