OpenRC is an alternate init system developed by Gentoo developers. OpenRC is a dependency based init system that works with the system provided init program, normally
/sbin/init. It is not a replacement for
OpenRC is available in the AUR. You can choose to install either AUR or AUR package. You will also need to install AUR (provides service files for use with openrc on arch) and AUR.
For booting with OpenRC add
init=/sbin/init-openrc to the kernel line in your bootloader configuration. If you want to go back to systemd replace it with init=/bin/systemd.
It is worth noting that the udev service is not enabled by default. In order to enable it:
#rc-update add udev default