API Version weirdness...

applied yaml

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: engage-ingress
  annotations:
    kubernetes.io/ingress.class: nginx-external
spec:
  rules:
  - host: engage.staging.example.com
    http:
      paths:
      - path: /
        backend:
          serviceName: engage
          servicePort: 80
  tls:
  - hosts:
    - engage.staging.example.com

kubectl get yaml

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"networking.k8s.io/v1beta1","kind":"Ingress","metadata":{"annotations":{"kubernetes.io/ingress.class":"nginx-external"},"name":"engage-ingress","namespace":"default"},"spec":{"rules":[{"host":"engage.playground.example.com","http":{"paths":[{"backend":{"serviceName":"engage","servicePort":80},"path":"/"}]}}],"tls":[{"hosts":["engage.playground.example.com"}]}}
    kubernetes.io/ingress.class: nginx-external
  creationTimestamp: "2020-05-06T00:56:19Z"
  generation: 1
  name: engage-ingress
  namespace: default
  resourceVersion: "145130300"
  selfLink: /apis/extensions/v1beta1/namespaces/default/ingresses/engage-ingress
  uid: 488bca0c-34cf-4122-a350-2bde500d0f3a
spec:
  rules:
  - host: engage.playground.example.com
    http:
      paths:
      - backend:
          serviceName: engage
          servicePort: 80
        path: /
  tls:
  - hosts:
    - engage.playground.example.com
status:
  loadBalancer:
    ingress:
    - hostname: a0901a268b2281examplee2ffbd16e2-7baadc2e29c1d5ab.elb.us-east-1.amazonaws.com

From Liggit in slack linked conversation above (for those who don't like to click on "one-weird-trick" links to slack conversations:

kubectl get ingress is ambiguous and prefers the first ingress resource found in APIs listed in discovery, which is extensions/v1beta1 for backwards compatibility
kubectl get ingress.v1beta1.networking.k8s.io fetches the same resource in the new API group
the API server can translate any persisted ingress resource into either version and returns it in the version you request
you can add --v=6 to the kubectl invocation you see the actual URLs being requested

discovery is dynamic
so as soon as the server is not serving extensions/v1beta1 ingress, kubectl will prefer the networking.k8s.io version
and since the extensions/v1beta1 days, we now put the most stable version first in discovery
so unqualified kubectl get ingress kubectl invocations will get v1 ingress (once extensions/v1beta1 is gone)
extensions/v1beta1 was the exception where a beta version had higher priority, because people hadn't started writing version-aware kubectl invocations yet (because we hadn't given them a way to at that point)

See also: https://github.com/FairwindsOps/pluto#purpose

• API dynamic nature explained: kubernetes/kubernetes#58131 (comment)
• k8s Deprecation policy: https://kubernetes.io/docs/reference/using-api/deprecation-policy/