Setup behind caddy proxy

[foostuff]

I installed CD via pip on a debian bullseye machine but I am struggling with the caddy reverse proxy:
My browser always tries to access the css files etc in the ROOT directory. Like in https://gitmemory.cn/repo/dgtlmoon/changedetection.io/issues/221
But I can't get it to work even including the header_up X-Forwarded-Prefix /cd.io(/)

My Caddy config:

my.server.url {
	rewrite /cd.io /cd.io/
	route /cd.io/* {
		uri strip_prefix /cd.io
		reverse_proxy localhost:5000 {
			header_up X-Forwarded-Prefix /cd.io
		}
	}
}

Starting CD:

$ changedetection.io -d /mnt/samsung_ssd/changedetection -p 5000
Watching: 9d83978b-a850-4e42-ac10-9287d6ab1d20 http://www.quotationspage.com/random.php
Watching: 9c76bd6e-40cd-45ca-8a1b-690fe5a2f59f https://news.ycombinator.com/
Watching: 72d3bb5c-ddd3-417b-8409-ceb34792588d https://www.gov.uk/coronavirus
Watching: 44818c0f-0511-4c22-b553-2648bed4f737 https://changedetection.io
(16622) wsgi starting up on http://0.0.0.0:5000
(16622) accepted ('127.0.0.1', 33268)
93.232.***.***,127.0.0.1 - - [03/Jan/2022 14:16:53] "GET / HTTP/1.1" 200 10931 0.035382

Any help would be appreciated.