I recently installed and Antergos and when Gnome started up the UI elements were shown in German. When I tried to change the UI Language there were no other languages than German available
But don't worry, this can be easily fixed as described very well in the ArchLinux Wiki by simply enabling the required languages in the file
[[email protected]]$ sudo locale-gen Generating locales... de_CH.UTF-8... done en_US.UTF-8... done es_AR.UTF-8... done Generation complete.
Now you can choose the selected languages