Ah thanks. I added `(shepherd-requirement '(radicale))` to my nginx-configuration. Sadly the issue is not fixed, the situation is the same as before.
I assume that radicale takes a fracture of a second to start. And nginx starts faster up. See this small experiment: $ sudo herd stop radicale $ sudo herd start radicale; curl localhost:5232 Service radicale has been started. curl: (7) Failed to connect to localhost port 5232 after 0 ms: Verbindungsaufbau abgelehnt $ sudo herd stop radicale $ sudo herd start radicale; sleep 0.2; curl localhost:5232 Service radicale has been started. Redirected to /.web