I’ll start by plugging Harvard’s free courses catalog as well as Udemy
Edit: Gonna add 2 more I remembered-
Blender - I wish I had more time to learn it, but I did start the infamous “Donut Tutorial” once!
Watch Cartoons Online - Lots of good older stuff!
Docker is a program that runs on an OS, usually Linux, and the docker apps or images are run by docker on the OS docker is installed on.
I’m a rookie, but I run TrueNAS which runs docker images. Previously I ran plain Debian with docker installed to run docker images.