(I am the author of the Cloudron package)
Testing this with the URL posted above:
$ curl -X HEAD -v https://n8n.bazo.dk/webhook/apsis_feed_1
...
< HTTP/2 404
< server: nginx
< date: Sat, 11 Mar 2023 11:08:39 GMT
Note that it responds with something with a GET. So, I am not sure this is CORS related (in both cases, Origin header is unset).