It is possible to use CNI plugins that are not directly supported by the KubeOne. Here’s an example for Flannel.
apiVersion: kubeone.k8c.io/v1beta2
kind: KubeOneCluster
versions:
  kubernetes: 1.33.2
clusterNetwork:
  cni:
    external: {}
addons:
  addons:
  - name: default-storage-class
helmReleases:
  - chart: flannel
    repoURL: https://flannel-io.github.io/flannel/
    namespace: kube-system
    version: v0.27.0