Gentoo also makes me think about combinatorial explosion of configuration options. Even if we restrict to 64-bit x86, there's glibc vs. musl libc, systemd vs. OpenRC, desktop vs. non-desktop, GNOME vs. KDE vs. Xfce, system hardening, and that's without getting into all the USE flags you can toggle individually.
Fortunately, Gentoo provides a stage3 to start with configured with systemd and desktop, so I got Rust, GCC, GTK 3, etc. prebuilt and only needed to add Xfce and some Xorg meta packages.