At some point somebody's gonna make a distro that's just Systemd and a kernel.
Would be the ultimate base OS.
But it's not so easy. I actually looked into all the dependencies of a Linux system and it turns out to be an extremely entangled monolith at the core. Everything depends on everything. So you actually can't have "just a kernel and systemd as 'user-land'".
Any resources for this ? Most books I've read/seen are either about Linux kernel internals or using userspace Linux. I'd like to know more about what actually goes into making a complete usable distro.