flux2/manifests/policies/allow-acme.yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-acme
spec:
  ingress:
  - from:
    - namespaceSelector: {}
    ports:
      - protocol: TCP
        port: 8089
  podSelector:
    matchLabels:
      acme.cert-manager.io/http01-solver: 'true'
  policyTypes:
  - Ingress