linux-api-headers isn't replaced by linux-libre-api-headers when migrating from archlinux x86_64 to parabola x86_64 systemd.
pacman -Qm shows it still installed, to fix it manually, run these in order as root:

pacman -S linux-libre-api-headers --overwrite "*"
pacman -R linux-api-headers
pacman -S linux-libre-api-headers --overwrite "*"