Steps to reproduce:

1. Make sure that neither LANG nor any LC_* variables are set
2. Run: export LANGUAGE="en_US:de:fr" (or set this language order in KDE's
language settings)
3. Run: kdesu yast2

Expected result:

Since English is the first language, Yast2 should be in English.

Actual result:

Yast2 is in German!

More info:

If you do:
- export LANGUAGE="en_US"
- kdesu yast2
Yast2 will be in English.

It seems zypper is also affected partially.
When LANGUAGE="en_US:de:fr" then zypper is in English, but the confirmation
prompt is in German:

Overall download size: 682.1 MiB. Already cached: 0 B  After the operation,
additional 753.3 MiB will be used.
Fortfahren? [j/n/? zeigt alle Optionen] (j):


Could be a duplicate of https://bugzilla.opensuse.org/show_bug.cgi?id=843573
but that one didn't have any details.