- Kubeadm: added the experimental (alpha) feature gate `EtcdLearnerMode` that allows etcd members to be joined as learner and only then promoted as voting members ([#113318](https://github.com/kubernetes/kubernetes/pull/113318), [@pacoxu](https://github.com/pacoxu))

- `kubeadm`: promoted feature gate `EtcdLearnerMode` to `beta`. Learner mode for
  joining `etcd` members is now enabled by default. ([#120228](https://github.com/kubernetes/kubernetes/pull/120228), [@pacoxu](https://github.com/pacoxu))

* Websocket requests may now authenticate to the API server by passing a bearer token in a websocket subprotocol of the form `base64url.bearer.authorization.k8s.io.<base64url-encoded-bearer-token>`. ([#47740](https://github.com/kubernetes/kubernetes/pull/47740), [@liggitt](https://github.com/liggitt))

- The helping message of commands which have sub-commands is now clearer and more instructive. It will show the full command instead of `kubectl <command> --help ...`
  

- kubeadm: fixed ignoring errors when pulling control plane images ([#80529](https://github.com/kubernetes/kubernetes/pull/80529), [@bart0sh](https://github.com/bart0sh))
- Fix a bug in kube-addon-manager's leader election logic that made all replicas active. ([#80575](https://github.com/kubernetes/kubernetes/pull/80575), [@mborsz](https://github.com/mborsz))

* Use separate client for leader election in scheduler to avoid starving leader election by regular scheduler operations. ([#53793](https://github.com/kubernetes/kubernetes/pull/53793), [@wojtek-t](https://github.com/wojtek-t))

* Updated priority of mirror pod according to PriorityClassName. ([#58485](https://github.com/kubernetes/kubernetes/pull/58485), [@k82cn](https://github.com/k82cn))

* kube-scheduler: restores default leader election behavior. Setting the `--leader-elect`  command line parameter to `true` ([#60524](https://github.com/kubernetes/kubernetes/pull/60524), [@dims](https://github.com/dims))

- The PodDisruptionBudget API has been promoted to policy/v1 with no schema changes. The only...

- Updated the default API priority-and-fairness config to avoid endpoint/configmaps operations from controller-manager to all match leader-election priority level. ([#106725](https://github.com/kubernetes/kubernetes/pull/106725), [@wojtek-t](https://github.com/wojtek-t))

* kube-scheduler: restores default leader election behavior. leader-elect command line parameter should "true" ([#60524](https://github.com/kubernetes/kubernetes/pull/60524), [@dims](https://github.com/dims))