> Or can you recommend alternative resources?
Understanding OSes better by understanding a particular OS better is part of the reason why I moved from Windows to Ubuntu to Archlinux. Having your whole OS being open source (Windows -> Ubuntu) and using an OS that doesn't try to add a bunch of superfluous infrastructure over what's actually needed (Ubuntu -> Archlinux) makes understanding the system much easier.
As an alternative resource, I suggest installing Archlinux, read the documentation of the base system (manpages, info manuals, the Archlinux wiki, online documentation on particular projects like https://x.org/ for xorg/x11 documentation, etc.), experiment with it, see how it's built, look into the source code of anything you want to know in detail.
Also, there's the LFS (Linux From Scratch) project, which teaches you how to build a Linux distro without depending on an installation .iso. You get to download, build, and install the kernel from kernel.org, glibc from gnu.org, etc.