I would like have some proficient understanding over the architecture of Linux. Both in terms of how the kernel works, and how everything is configured up to us

I would like have some proficient understanding over the architecture of Linux. Both in terms of how the kernel works, and how everything is configured up to userspace. I'm inclined to go the systemd route because I use it myself regularly, but I also understand that systemd is a bit of a monolithic piece within Linux. I suspected that it might hide a lot of things that used to be more discrete and manual (but more unix-y).