Comment # 1 on bug 1118870 from Wolfgang Bauer

What's the full output when you run "locale" in a terminal window (konsole
e.g.) inside the graphical session?

Also (assuming you actually use KDE/Plasma as desktop), please provide the
content of the file ~/.config/plasma-locale-settings.sh .

This is likely not a bug, but rather a "messed up" locale config (probably not
using UTF-8) IMHO...