the material we learned from was mostly the manpages (start with "man intro" and explore as your curiosity dictates), and the HOWTOs from the Linux documentation project. both these resources still exist; they are not very current... but a lot of the tooling hasn't changed all that much either, so it's still the best we have to point anyone towards.

we've had this question before as well, whether there's any accessible material that helps people get started. we'd particularly love to hear about anything that's especially pitched to the queer community or to a young audience. we think that could be an amazing way to drive change in the world. let us know!

the map is the territory is a good short introduction to Bash with a very magical theme, which is probably either very cool or distracting from the lesson depending on one's own attitude towards it. I think it's neat.