It happened to me on Arch during the switch from init to systemd.
Update was documented, but I didn’t look. Did my `pacman -syua` as I normally did on a daily, and rebooted to a totally borked system. This is when I was a grad student and really needed that laptop that week.
I still love Arch, but I can’t trust it anymore as a daily driver.
I have used Arch as my main system for 6 years now (was Gentoo before) and never had anything of the sort.
How does this even happen?