Comment 4 for bug 1674931

As a workaround, you need to install "language-package-gnome-XX" for the language you want (or use the language-selector-gtk tool to do it for you). Then the language should be available in Unity8 system-settings.

The only "pre-installed" language pack for the ISO is I think English, and whatever language you select in the installer.

To make a decision about getting rid of langpacks (which really, is going to basically be necessary for snaps anyway), we need an analysis of size difference in packages and how much extra disk space would be used by having all the translations for all default apps, always installed. And to convince Ubuntu Release Team and maybe Tech Board to get it done.