Dropping this for the people asking / wondering where to start with Linux before they feel comfortable attempting easy boxes.
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Linux Basics for Hackers by OccupyTheWeb, uses Kali as the learning environment and is one of the more practical intros out there.
[URL unfurl="true"]https://limewire.com/d/V5sKB#g1a555Qctp[/URL]
It covers stuff that directly maps to what you'll run into on easy/medium machines (permissions, log manipulation, service enumeration, scripting. Good for building muscle memory on the command line)
IMO a solid foundation if you're still shaky on the fundamentals. Pair it with TryHackMe's Linux paths or just go straight to HTB Starting Point after. Idk, you do you.