

https://www.lpi.org/our-certifications/lpic-1-overview/
Free PDFs, touches on the topics and actually shows you the commands, gives you exercises + further info. It will never be an end-all-be-all but it’s a start if you’re looking to learn something. It really all depends on what you’re trying to get out of it I figure. If you’re trying to be a sysadmin, then everybody else will have a different answer.
I don’t dare do hardcore gaming on Linux 'cause I’m lazy. I went and bought a Raspberry Pi at some point and only tried out some distros on it. I had troubles from day 1 where like OP, I could figure out. Right now, I can’t even get Redshift to work on basically a RaspberryPi OS fork and I have no clue why.