- Restores compatibility with <=1.15.x custom resources by not publishing OpenAPI for non-structural custom resource definitions ([#82653](https://github.com/kubernetes/kubernetes/pull/82653), [@liggitt](https://github.com/liggitt))

* CustomResourceDefinitions: OpenAPI v3 validation schemas containing `$ref`references are no longer permitted. Before upgrading, ensure CRD definitions do not include those `$ref` fields. ([#58438](https://github.com/kubernetes/kubernetes/pull/58438), [@carlory](https://github.com/carlory))

</pre>

<p>
<code>B0</code> and <code>B1</code> are different because they are new types
created by distinct <a href="#Type_definitions">type definitions</a>;
<code>func(int, float64) *B0</code> and <code>func(x int, y float64) *[]string</code>
are different because <code>B0</code> is different from <code>[]string</code>;

- Ingress:
  - `spec.ingressClassName` replaces the deprecated `kubernetes.io/ingress.class` annotation, and allows associating an Ingress object with a particular controller.

  - The OpenAPI definitions with the prefix "io.k8s.kubernetes.pkg" (deprecated since 1.9) have been removed. ([#74596](https://github.com/kubernetes/kubernetes/pull/74596), [@sttts](https://github.com/sttts))

- OpenAPI definitions served by kube-apiserver now include enum types by default. ([#108898](https://github.com/kubernetes/kubernetes/pull/108898), [@jiahuif](https://github.com/jiahuif))

* CustomResourceDefinitions: OpenAPI v3 validation schemas containing `$ref`references are no longer permitted (valid references could not be constructed previously because property ids were not permitted either). Before upgrading, ensure CRD definitions do not include those `$ref` fields. ([#58438](https://github.com/kubernetes/kubernetes/pull/58438), [@carlory](https://github.com/carlory))

- `kubectl rollout restart` now works for DaemonSets and StatefulSets. ([#77423](https://github.com/kubernetes/kubernetes/pull/77423), [@apelisse](https://github.com/apelisse))
- `kubectl get --watch=true` now prints custom resource definitions with custom print columns. ([#76161](https://github.com/kubernetes/kubernetes/pull/76161), [@liggitt](https://github.com/liggitt))

- The `batch/v2alpha1` CronJob type definitions and clients are deprecated and removed. ([#96987](https://github.com/kubernetes/kubernetes/pull/96987), [@soltysh](https://github.com/soltysh)) [SIG API Machinery, Apps, CLI and Testing]

- API paging is now enabled for custom resource definitions, custom resources and APIService objects. ([#67861](https://github.com/kubernetes/kubernetes/pull/67861), [@liggitt](https://github.com/liggitt))