I tried to study a bit from beej.us and I appreciated the style of teaching, but ultimately thought it wasn’t for me as it didn’t go much into depth and focused more on creating C programs. Is there some source from where I can learn in a comprehensive yet easy to understand manner the fundamentals of computer networking, at least to the extent that is relevant for selfhosting?
Cisco offers a whole lot of free online training as well, on several different websites.
Its kind of a pita to get access in the first place, but its definitely free, comprehensive, and starts from the ground up.
And of course, they have paid training options on those same sites.