Here's a tl;dr of my Linux learning curve -- from 0 (Windows pleb) to hero:
Start with a "user-friendly" distro (Linux Mint, ZorinOS) and get used to its package manager (i.e How to install, uninstall and remove stuff. Also, your best friend.).
Then go for a more "serious" distro like Debian. And from Debian... Arch. Keep at it until you've got the most interesting commands (and "whom is whom" regarding video graphics, audio, etc... the "basic" stuff) written on your forehead.
After that, "duckduckgo" about "Minimal linux installation" or "Baremetal linux installation". Follow the instructions closely and at heart. PS: You are gonna suffer a bit.... but that is perfectly fine. Once again, you are gonna have to get used to it and to witness "your own distro" booting up for the first time. Yes, the nerdgasm feels quite great.
At this point, there is nothing "much" to learn other than to add more "depth" to the stuff you learned by "duckduckgo" about "Linux how do I improve my network", "Linux how to improve performance", etc until you are used to all that.
Now, you've reached the "average user" status and there is nothing "strictly necessary" to learn -- so start your own github, send your .dotfiles/scripts in, and go take a break. Congrats, you are now a penguin.