before all of this tanks and any interaction on the web worth having becomes impossible (already is kind of the case)

WHAT ARE THE FUNDAMENTAL CONCEPTS of OS and system programming/networking worth digging extra deep into to stay based and off the grid (i.e. info spooks are happy zoomers dont know)

suggest books too, both old (classics) and up to date ones that will serve me well a decade from now. I know how to program well enough but only starting to get into the linux and systems programming deeply

networking especially, and is cryptography is even worth learning ? I have a background in physics if that matters at all