> understood how one would go from here to a modern distro

Well, after LFS you go to BLFS. Compiling KDE isn't that hard if you use scripts that help you. The big problem I see is that a lot of information is missing. People need to know a whole lot. But if you managed to compile it, a simple "startx" should work fine. I even got KDE plasma to work on wayland. Wayland gives me fewer options than xorg though, so I went back to xorg.