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).
For homelab, start with the absolute basics - setup a firewall, and make sure you understand how it works! Map out your network topology, even if it is just your DSL box, router & your PC + printer with a raspberry pi (or 2) for your project.
After you've made absolutely sure that the outside world can only get in where you've let it, then you can focus on having good application-level security; unfortunately this is really case-by-case.
As for resources, I would start with YouTube - you tend to get to focus your learning a bit better and spend less time searching for something relevant (as you mentioned, enterprise tends to be the focus, because they're often the main targets of network related attacks). For more depth, but not crazy detail, try the O'Reilly books or similar on networks & related security topics (there are a few!)
One more thing - install Wireshark and get a real-time view of what your network is doing. Massively helpful tool.