There are several official responses now to help us understand this deprecation.
K8sContributors on Twitter: "#Kubernetes 1.20 introduces an important change to the kubelet - the deprecation of #Docker as a container runtime option. What does this mean and why is it happening? You can learn more in our blog post! https://t.co/lzPPzwXUNM" / Twitter - https://twitter.com/K8sContributors/status/13343017328309903...
Don't Panic: Kubernetes and Docker | Kubernetes - https://kubernetes.io/blog/2020/12/02/dont-panic-kubernetes-...
Dockershim Deprecation FAQ | Kubernetes - https://kubernetes.io/blog/2020/12/02/dockershim-faq/