Looks like this site may go into some more detail of how the specific packages interact to create a "standard" Linux distribution more than the LFS series does; but I'm not sure how much has changed regarding that in recent times... Even the faded BLFS book I was gifted in 6th grade seems to be more focused on just getting the packages built and installed into the LFS root than going in depth about their internals/function. Even though tools like buildroot/OE/Yocto offer much better tools to make a Linux from scratch, I think both of these offer a great way to quickly gain at least some insight into Linux + userspace