Need help with understanding native linux

I’m asking your help to provide me useful free sources (websites) that can help me understand the following errors that can occur from: Selinux, journalctl, dmesg, etc.
I don’t want to use AI to fix issues.
I want to learn how to troubleshoot, and understand the error’s that i encounter, because using AI isn’t gonna help me thus I won’t be able to help the community with their errors or linux problems.

So, the sources that i prefer you provide will help me with the following:

  • Understanding errors
  • Knowing when to use system commands to troubleshoot errors and when not to.
  • Understanding SeLinux for security
  • Useful commands to learn and understand
  • Fully understanding bash (I only know If statements, read statements, and while loops)
  • Fully understanding Regular Expressions (Really help with commands like grep)

Backstory:
I used containerized environments from sites like: gitpod.io, shell.cloud.google.com, codesandbox.io, github codespaces, and other free IDEs to learn linux, but i started and discovered linux on a chromebook. So, i never really had any experience with Native linux but some experience with Kali linux virtualized, but that’s about it.

Started using linux natively May 24th.

I find the Gentoo docs very useful for SELinux. (Most of it is not distro-specific, so it’s still useful on Fedora.)

For shell stuff, The Linux Command Line by William Shotts (Creative Commons license, free PDF available from that link) is often recommended.