- deprecate the usage of the experimental flag '--use-api' under the 'kubeadm alpha certs renew' command. ([#88827](https://github.com/kubernetes/kubernetes/pull/88827), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

   * files with extension "PSB" are in a distinct but related format).
   *
   * <p>This is a more recent replacement for the older, experimental type {@code x-photoshop}: <a
   * href="http://tools.ietf.org/html/rfc2046#section-6">RFC-2046.6</a>.
   *
   * @since 15.0
   */

* Fixed 'Schedulercache is corrupted' error in kube-scheduler ([#55262](https://github.com/kubernetes/kubernetes/pull/55262), [@liggitt](https://github.com/liggitt))
* Fix hyperkube kubelet --experimental-dockershim ([#55335](https://github.com/kubernetes/kubernetes/pull/55335), [@ivan4th](https://github.com/ivan4th))

- Updated `kubeadm` to use the `InitialCorruptCheck=true` etcd feature gate instead of the deprecated `--experimental-initial-corrupt-check` flag. Also replaced the use of `--experimental-watch-progress-notify-interval` with its graduated counterpart `--watch-progress-notify-interval`. ([#132838](https://github.com/kubernetes/kubernetes/pull/132838), [@AwesomePatrol](https://github.com/AwesomePatrol))...

- HA improvements:
  - `kubeadm join --experimental-control-plane` can now be used to join control plane instances to an existing cluster.
  - `kubeadm upgrade node experimental-control-plane` can now be used for upgrading secondary control plane instances created with `kubeadm join --experimental-control-plane`.
Multi-arch support (EXPERIMENTAL):

*   You now have the option to use CoreDNS instead of KubeDNS. To install CoreDNS instead of kube-dns, set CLUSTER_DNS_CORE_DNS to 'true'. This support is experimental. ([#52501](https://github.com/kubernetes/kubernetes/pull/52501),[ @rajansandeep](https://github.com/rajansandeep)) ([#55728](https://github.com/kubernetes/kubernetes/pull/55728),[ @rajansandeep](https://github.com/rajansandeep))

## Urgent Upgrade Notes
### (No, really, you MUST read this before you upgrade)
#### Cluster Lifecycle
- Kubeadm: add a new `kubelet-finalize` phase as part of the `init` workflow and an experimental sub-phase to enable automatic kubelet client certificate rotation on primary control-plane nodes.

- Kubeadm: support experimental JSON/YAML output for `kubeadm upgrade plan` with the `--output` flag. ([#108447](https://github.com/kubernetes/kubernetes/pull/108447), [@pacoxu](https://github.com/pacoxu))

- Kubeadm: add the flag "--experimental-initial-corrupt-check" to etcd static Pod manifests to ensure etcd member data consistency ([#109076](https://github.com/kubernetes/kubernetes/pull/109076), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

GlobalMemoryStatusEx to get total physical memory on windows nodes. ([#57124](https://github.com/kubernetes/kubernetes/pull/57124), [@JiangtianLi](https://github.com/JiangtianLi))

* Windows containers now support experimental Hyper-V isolation by setting annotation `experimental.windows.kubernetes.io/isolation-type=hyperv` and feature gates HyperVContainer. At the moment this function only supports one container per pod. ([#58751](https://github.com/kubernetes/kubernetes/pull/58751), [@feisk...