- https://github.com/kubernetes-sigs/kustomize/pull/4911: Drop support for a very old, legacy style of patches. patches used to be allowed to be used as an alias for patchesStrategicMerge in kustomize v3. You now have to use patchesStrategicMerge explicitly, or update to the new syntax supported by patches. See examples in the PR description of https://github.com/kubernetes-sigs/kustomize/pull/4911.

- The deprecated flag --experimental-kustomize is now removed from kubeadm commands. Use --experimental-patches instead, which was introduced in 1.19. Migration information available in --help description for --experimental-patches. ([#94871](https://github.com/kubernetes/kubernetes/pull/94871), [@neolit123](https://github.com/neolit123))

## Changes to API Resources
### ABAC
* ABAC policies using `"user":"*"` or `"group":"*"` to match all users or groups will only match authenticated requests. To match unauthenticated requests, ABAC policies must explicitly specify `"group":"system:unauthenticated"` ([#38968](https://github.com/kubernetes/kubernetes/pull/38968), [@liggitt](https://github.com/liggitt))

  The scheduling hints allow the scheduler to only retry scheduling a `Pod`
  that was previously rejected by the `NodeAffinity` plugin if a new `Node` or a `Node` update matches the `Pod`'s node affinity. ([#119155](https://github.com/kubernetes/kubernetes/pull/119155), [@carlory](https://github.com/carlory))
- `kubeadm`: promoted feature gate `EtcdLearnerMode` to `beta`. Learner mode for

  - `priority_level_seat_count_watermarks` is removed.
  - `priority_level_request_count_samples` is replaced with `priority_level_request_utilization`, which samples every nanosecond rather than every millisecond; the old metric conveyed utilization despite its name.

### (No, really, you MUST read this before you upgrade)

- Kubeadm: remove the deprecated flag `--experimental-patches` for the `init|join|upgrade` commands. The flag `--patches` is no longer allowed in a mixture with the flag `--config`. Please use the kubeadm configuration for setting patches for a node using `{Init|Join}Configuration.patches`. ([#104065](https://github.com/kubernetes/kubernetes/pull/104065), [@pacoxu](https://github.com/pacoxu))

### Other notable changes

* Connections from Pods to Services with 0 endpoints will now ICMP reject immediately, rather than blackhole and timeout. ([#72534](https://github.com/kubernetes/kubernetes/pull/72534), [@thockin](https://github.com/thockin))
* Services of type=LoadBalancer which have no endpoints will now immediately ICMP reject connections, rather than time out. ([#74394](https://github.com/kubernetes/kubernetes/pull/74394), [@thockin](https://github.com/thockin))

- Kube-proxy now trims extra spaces found in loadBalancerSourceRanges to match Service validation. ([#94107](https://github.com/kubernetes/kubernetes/pull/94107), [@robscott](https://github.com/robscott)) [SIG Network]

 - The flag `--experimental-patches` is now deprecated and will be removed in a future release. You can migrate to using the new flag `--patches`. Add a new field `{Init|Join}Configuration.patches.directory` that can be used for the same purpose. For `init` and `join` it is now recommended that you migrate to configure patches via `{Init|Join}Configuration.patches.directory`. For the time being, these flags can be mixed with `--config`, but that...

- Azurefile: Normalize share name to not include capital letters ([#100731](https://github.com/kubernetes/kubernetes/pull/100731), [@kassarl](https://github.com/kassarl)) [SIG Cloud Provider and Storage]
- EndpointSlice IP validation now matches Endpoints IP validation. ([#101084](https://github.com/kubernetes/kubernetes/pull/101084), [@robscott](https://github.com/robscott)) [SIG Apps and Network]