I had to add a few more labels to my docker:
- traefik.http.middlewares.cors.headers.customResponseHeaders.Access-Control-Allow-Origin=*
- traefik.http.middlewares.cors.headers.customResponseHeaders.Access-Control-Allow-Methods=GET, POST, OPTIONS
- traefik.http.middlewares.cors.headers.customResponseHeaders.Access-Control-Allow-Headers=DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Authorization
- traefik.http.routers.n8n.middlewares=cors@docker