NetworkPolicy adjustment for k3s and Traefik

k3s, k3OS, and k3d
1

We are running a Helm App on Rancher through Kubernetes since a long time and always used the following NetworkPolicy:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: nwpolicy
  namespace: {{ .Release.Namespace }}
spec:
  podSelector: {}
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          name: {{ .Release.Namespace }}
    - ipBlock:
        cidr: 10.42.2.0/32
    - ipBlock:
        cidr: 10.42.1.0/32
  policyTypes:
    - Ingress

This allows communication from certain nodes (seen in the ipBlock parts) and the App’s own namespace’s objects (seen in the namespaceSelector part) between each other. The purpose of this NetworkPolicy is that only what belongs to this namespace is supposed to be able to talk to other object in this namespace. Objects from other namespaces should never be allowed to communicate with objects of this specific namespace.

So, usually nginx is the default ingress that is used within Rancher, which the NetworkPolicy always worked with and still works, right in this moment.
K3s on the other hand, seems to use Traefik by default. That blocks the previously allowed traffic from arriving on the destination pods in the example namespace referenced above. It is unclear what exactly causes the difference in behaviour.

How does the NetworkPolicy need to be adjusted to make this work?