Traefik router middleware to GCS bucket [redirectRegex]

Traefik Traefik v2
1

So I've created a GCS bucket, with a simple index.html file inside;

$ gsutil mb gs://my.bucket.com
$ gsutil cp index.html gs://my.bucket.com
$ gsutil web set -m index.html gs://my.bucket.com
$ gsutil iam ch allUsers:objectViewer gs://my.bucket.com

and I can access the index.html under: https://storage.googleapis.com/my.bucket.com/index.html

Now I would like to create a Traefik router in k8s cluster and us it with ingress object, like:

apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
  name: my.bucket.com-redirect
spec:
  redirectRegex:
    regex: ^https://my.bucket.com/(.*)
    replacement: https://storage.googleapis.com/my.bucket.com/${1}
    permanent: true
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my.bucket.com-ingress
  annotations:
    traefik.ingress.kubernetes.io/router.middlewares: "mynamespace-my.bucket.com-redirect@kubernetescrd"
spec:
  ingressClassName: traefik
  tls:
    - hosts:
      - my.bucket.com
      secretName: sedcret-name
  rules:
  - host: my.bucket.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            # This is not actually used by needed to validate manifest
            name: placeholder
            port:
              number: 80

The DNS is set in place, and requests to my.bucket.com are visible in traefik logs, but it is always 404 (when I specify / or index.html)
(The SSL certificate is added correctly also, not sure if that is relevant)

What am I missing? What might be blocking this or causing 404 error?