Organizr on Caddy v2

I would also be really interested in a solution while running organizr on a docker container. With Caddy v1, it used to work only on the local network as follows:

reverse_proxy /organizr/ http://organizer_IP:port {
without /organizr
transparent
header_upstream Host {host}
}

I have converted this to Caddy v2 as follows, but it doesn’t even work on the local network (I get 404 Not Found, nginx/1.14.2)

reverse_proxy /organizr/ http://organizer_IP:port {
	header_up Host {host}
}