Ask your Linux group. Seriously. They should know best what kinds of issues their ‘users’ frequently face and what kind of information there is.
I learned Linux by doing. Set up a webserver, set up a network share, assemble a RAID with 2 old HDDs. Install Steam and play around a bit. Try LaTex and write your next homework assignment with it. Set up a Python / R / C++ development environment. All of that is good practice and you’ll understand the concepts and specific issues once you do it yourself. Imho that’s better than a theoretical course. You can do this in VMs or find old hardware. Some people in such groups have good connections.
Also a university library should have some free (for you) material (books) on Linux.