I think the unifi package is currently missing, perhaps accidentally. If I search Packages from the website, it appears here:
https://archlinuxarm.org/packages/any/unifi
And has been updated recently (about 2 weeks ago).
However, when I look at a mirror, it's not listed where I would expect it. For example, it's missing here:
http://ca.us.mirror.archlinuxarm.org/armv6h/community/
And when I run pacman -S unifi, it says:
"error: target not found: unifi"