* `--feature-gates` argument has been removed from the `kubeadm join` command. Feature gates will be retrieved from the cluster configuration during the join process. ([#70755](https://github.com/kubernetes/kubernetes/pull/70755), [@ereslibre](https://github.com/ereslibre))

- The `kubeadm join` command can now be used in phases. Similar to the work that was done for `kubeadm init` in 1.13, in 1.14 the `join` phases can be now executed step-by-step/selectively using the `kubeadm join phase` sub-command. This makes it possible to further customize the workflow of joining nodes to the cluster.
kubernetes/kubeadm: [#1204](https://github.com/kubernetes/kubeadm/issues/1204)

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 might change in the future. On a command line, the last *patches...

* `kubeadm join` is now blocking on the kubelet performing the TLS Bootstrap properly. Earlier, `kubeadm join` only did the discovery part and exited successfully without checking that the kubelet actually started properly and performed the TLS bootstrap correctly. Now, as kubeadm runs some post-join steps (for example, annotating the Node API object with the CRISocket), `kubeadm join` is now waiting for the kubelet to perform the TLS Bootstrap,...

- Kubeadm: warn but do not error out on missing "ca.key" files for root CA, front-proxy CA and etcd CA, during "kubeadm join --control-plane" if the user has provided all certificates, keys and kubeconfig files which require signing with the given CA keys. ([#94988](https://github.com/kubernetes/kubernetes/pull/94988), [@neolit123](https://github.com/neolit123)) [SIG Cluster...

* kubeadm: Fix a bug where if couple of CRIs are installed a user override of the CRI during join (via kubeadm join --cri-socket ...) is ignored and kubeadm bails out with an error ([#76505](https://github.com/kubernetes/kubernetes/pull/76505), [@rosti](https://github.com/rosti))

* kubeadm: Fix a bug where `kubeadm join` would wait 5 seconds without doing anything. Now `kubeadm join` executes the tasks immediately. ([#48737](https://github.com/kubernetes/kubernetes/pull/48737), [@mattmoyer](https://github.com/mattmoyer))

- Kubeadm: fix a whitespace issue in the output of the "kubeadm join" command shown as the output of "kubeadm init" and "kubeadm token create --print-join-command" ([#97413](https://github.com/kubernetes/kubernetes/pull/97413), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

- Kubeadm: during join when a check is performed that a Node with the same name already exists in the cluster, make sure the NodeReady condition is properly validated ([#89602](https://github.com/kubernetes/kubernetes/pull/89602), [@kvaps](https://github.com/kvaps)) [SIG Cluster Lifecycle]

- 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):