Good content for learning computer science?

I am speaking specifically to the subset of people who learn stuff as a hobby and know the excitement of finding a good youtube channel that has lots of videos on advanced stuff without dumbing down. I know its a rare person who relates to what I'm talking about here so if you're reading this and you have some good sources that you've liked in the past please share. I like security stuff, systems programming, networking stuff, but will settle for anything generally computer sciency that is good quality. Thanks :)