Running docker scan <image> returns an error on ubuntu 20.04

When I tried scanning local images, like the hello-world image, using docker scan hello-world, I get this error

docker: 'scan' is not a docker command.
See 'docker --help'

My docker version is

Client: Docker Engine - Community
 Version:           20.10.2
 API version:       1.41
 Go version:        go1.13.15
 Git commit:        2291f61
 Built:             Mon Dec 28 16:17:43 2020
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

There is a plugin available:

Requirement: apt knows about the docker-repositories

This should be already fulfilled after following the install-guide at https://docs.docker.com/engine/install/ubuntu/

Example:

$ cat /etc/apt/sources.list.d/docker.list 
deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable

Installation:

$ sudo apt update
$ sudo apt install docker-scan-plugin

Running docker scan will reveal more requirements:

• login to Docker Hub
• consent to access Snyk (For more information search the web for docker Snyk.)

$ docker scan hello-world
Docker Scan relies upon access to Snyk, a third party provider, do you consent to proceed using Snyk? (y/N)
y
failed to get DockerScanID: You need to be logged in to Docker Hub to use scan feature.
please login to Docker Hub using the Docker Login command