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?
Yup. And the official training books are still a great resource for learning everything from the basics to more advanced stuff.
I bought an updated set a couple of years ago, and they still hold up.
I still reference my Cisco Press CCIE routing TCP/IP volume 1 and 2 from 2005