- in /etc/pacman.conf uncomment (both lines):
[non_systemd]
Include = /etc/pacman.d/mirrorlist

Then you can get what you need, my case for lvm on luks:

pacman -Syu lvm2 lvm2-openrc cryptsetup cryptsetup-openrc alsa-utils alsa-utils-openrc cronie cronie-openrc

and back to the guide.