@Rzro Please open a terminal and enter the following command:
systemctl status avahi-daemon.service
Most probably, it’s ouput will tell you that the user “avahi” is missing in your system. This would be the same problem as described in the post that you found on archlinux.org. The solution references the install script which is supposed to get executed after avahi is installed (https://git.archlinux.org/svntogit/packages.git/tree/trunk/avahi.install?h=packages/avahi). I just installed Antergos and am experiencing the same problem.
In order to solve it, you just need to add the missing user and group using the commands given in the install script (using sudo):
sudo groupadd -r -g 84 avahi
sudo useradd -r -u 84 -g avahi -d / -s /bin/nologin -c avahi avahi