enable ssh on install media src

The simplest way is to

install Arch onto an USB stick/harddisk (you can do this from the live cd) in the new installation set a root password

passwd

allow ssh root login (vi /etc/ssh/sshd_config and append PermitRootLogin yes)

echo "PermitRootLogin yes" > /etc/ssh/sshd_config

enable sshd

systemctl enable sshd

also don't forget to enable systemd-networkd anything else you may need (like to preconfigure wifi) boot the new machine from the usb device