I am still very much a novice in the self-hosting space, Linux etc. having fairly recently switched from using macOS as my daily driver and not tinkering much at all.
One of the things that often confuses me is networking and making sure my setup is secure. This is currently holding me back from hosting more stuff locally that I would require access to from outside my home, as I am afraid I am doing something that could severely compromise my data. It can sometimes be difficult to follow explanations from more advanced users due to the many different components of networking and security, and different layers of abstraction, which prevents me from following completely. I might understand one particular case, but then be unable to make connections to another one. So I would want to research this more intensively, and ideally I would end up being able to easily understand the data flows - the paths the data takes (e.g. I make a HTTPS request to some server from my laptop, how is that traffic routed correctly through my local area network and later the wide area network), in what forms (i.e. different protocols, encryption layers etc.).
In communities like this, I see there are a lot of very knowledgeable people who maybe could recommended any resources that cover this from the basics and onto more advanced stuff? Maybe a textbook from a university course on ICT that is considered particularly good? A YouTube channel with great explanations and visualizations? I am looking both at home LAN and internet in general. Enterprise level networks are not very interesting to me (at the moment).
IMO, text book covers more on theory. Generally text book are outdated when it comes out due to relatively longer time required for preparation and publishing.
But a lot of the underlying technology is unchanged for a long time, right? So to get a deeper grasp of e.g. different protocols and data flows, I imagine it could at least be a good starting point.
The Wikipedia-article on the Internet protocol suite of course provides a lot of information on this, but my issue with learning from Wikipedia is that it provides a long article on one topic with tons of links, but often no natural flow to the next topic. This could lead to reading up on things in the wrong order, making the learning process more difficult that it has to be. A text book on the other hand, if written well, is more a curated set of texts that introduces topics in a logical order, so that a topic is not introduced until the required prerequisites have already been treated.
A YouTube-channel (or perhaps rather a YouTube-playlist) can also provide such a curated set of material, although in my experience these videos can often be a little to superficial to get any proper understanding of the subject. There are of course exceptions.
Your have a point.
In addition to the textbook, check out certificate oriented book like network+ and security+