Ask HN: Online Linux Course for Teen

My son wanted to build another PC, so I bought him the parts under the agreement that he'd turn it into a Linux box. (we didn't really need another PC in the house, but he wanted to build another) Christmas school holidays approaching quick -- wanted to find an interesting/useful online linux course for him to do during holidays. What are contemporary course recommendations? I've seen a lot of lame stuff, especially course that just cram lots of incantations down your throat. Any recommendations for a course that is interesting and sets up the initial seed that will allow him to later move in whatever direction he wants with it. (For example recently I heard him speculating perhaps the box could help him do streaming, etc)