- Kubeadm: external etcd endpoints passed in the `ClusterConfiguration` that have Unicode characters are no longer IDNA encoded (converted to Punycode). They are now just URL encoded as per Go's implementation of RFC-3986, have duplicate "/" removed from the URL paths, and passed like that directly to the `kube-apiserver`...

- Kubeadm: if an addon is disabled in the ClusterConfiguration, skip it during upgrade. ([#129429](https://github.com/kubernetes/kubernetes/pull/129429), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

## Dependencies

### Added

* kubeadm: Control plane component configs are separated into ClusterConfiguration sub-structs. ([#70371](https://github.com/kubernetes/kubernetes/pull/70371), [@rosti](https://github.com/rosti))

- Kubeadm: during "upgrade apply/diff/node", in case the `ClusterConfiguration.imageRepository` stored in the "kubeadm-config" `ConfigMap` contains the legacy "k8s.gcr.io" repository, modify it to the new default "registry.k8s.io". Reflect the change in the in-cluster `ConfigMap` only during "upgrade apply". ([#11034...

- Kubeadm: fixed a bug when performing validation on `ClusterConfiguration` networking fields. ([#112751](https://github.com/kubernetes/kubernetes/pull/112751), [@SataQiu](https://github.com/SataQiu))

* kubeadm: v1beta2 InitConfiguration no longer embeds ClusterConfiguration it it. ([#77739](https://github.com/kubernetes/kubernetes/pull/77739), [@rosti](https://github.com/rosti))