How to Deploy Control Plane Without Master Node Registration Using Kubeadm

I will try to address both of your questions.

1. Add --cloud-provider=external kubelet startup flag on all nodes

Where is this .NodeRegistration.KubeletExtraArgs and how do I change it for all nodes in the cluster?

KubeletExtraArgs are any arguments and parameters supported by kubelet. They are documented here. You need to use the kubelet command with a proper flags in order to modify it. Also, notice that the flag you are about to use is going to be removed in k8s v1.23:

--cloud-provider string The provider for cloud services. Set to empty string for running with no cloud provider. If set, the cloud provider determines the name of the node (consult cloud provider documentation to determine if and how the hostname is used). (DEPRECATED: will be removed in 1.23, in favor of removing cloud provider code from Kubelet.)

EDIT:

To better address your question regarding: .NodeRegistration.KubeletExtraArgs

These are also elements of the kubeadm init configuration file:

It's possible to configure kubeadm init with a configuration file instead of command line flags, and some more advanced features may only be available as configuration file options. This file is passed using the --config flag and it must contain a ClusterConfiguration structure and optionally more structures separated by ---\n Mixing --config with others flags may not be allowed in some cases.

You can also find more details regarding the NodeRegistrationOptions as well as more information on the fields and usage of the configuration.

Also, note that:

KubeletExtraArgs passes through extra arguments to the kubelet. The arguments here are passed to the kubelet command line via the environment file

kubeadm writes at runtime for the kubelet to source. This overrides the generic base-level configuration in the kubelet-config-1.X ConfigMap

Flags have higher priority when parsing. These values are local and specific to the node kubeadm is executing on.

EDIT2:

kubeadm init is supposed to be used only once when creating a cluster whenever you use it with flags or a config file. You cannot change the configs by executing it again with different values. Here you will find info regarding kubeadm and it's usage. Once the cluster is setup kubeadm should be dropped and changes be made directly to the static pod manifests.

2. Change the --service-cidr due to network requirements

This is more complicated. You could try to do this similarly like here or here but that approach is prone to mistakes and rather not recommended.

The more feasible and safer way would be to simply recreate the cluster with kubeadm reset and kubeadm init --service-cidr. The option to automatically change the CIDRs was not even expected from the Kubernetes perspective. So in short, the kubeadm reset is the way to go here.

The error log has your answer:

failed to run Kubelet: misconfiguration: kubelet cgroup driver: "systemd" is different from docker cgroup driver: "cgroupfs""

See Kubernetes documentation on how to configure acgroup driver