- 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))

* 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...

* 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))

* 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 ...`
  

- Fixes v1.17.0 regression in --service-cluster-ip-range handling with IPv4 ranges larger than 65536 IP addresses ([#86534](https://github.com/kubernetes/kubernetes/pull/86534), [@liggitt](https://github.com/liggitt)) [SIG Network]

* Add `metrics-port` to kube-proxy cmd flags. ([#72682](https://github.com/kubernetes/kubernetes/pull/72682), [@whypro](https://github.com/whypro))
* kube-apiserver: a request body of a CREATE/UPDATE/PATCH/DELETE resource operation larger than 100 MB will return a 413 "request entity too large" error. ([#73805](https://github.com/kubernetes/kubernetes/pull/73805), [@caesarxuchao](https://github.com/caesarxuchao))

- 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))

- Output for `kubectl describe podsecuritypolicy` is now kind specific and cleaner ([#101436](https://github.com/kubernetes/kubernetes/pull/101436), [@KnVerey](https://github.com/KnVerey))