I've been adding Docker 20.10 to Jenkins as a tool, but couldn't get it to work with docker-workflow's

docker.withTool('Docker $version') 

After debugging the issue, I've found out that the withTool function assumes the tool uses a /bin directory inside the tool directory, which it doesn't.

I've built a branch which circumvents this issue by adding both the 'root' of the tool as well as the /bin directory for backwards-compatibility:
https://github.com/FireDrunk/docker-workflow-plugin/commit/ee2e7cf17d4acd8411d8f38172c144956d8709fd

Installer used: https://download.docker.com/linux/static/stable/x86_64/docker-20.10.6.tgz