I need a few non english fonts. Using the font installer in KDE, I installed a few ttf fonts.

Strangely, these fonts are used by browsers, but not by any other application. Selecting the font for use in Kwrite, GIMP and Scribus all result in english characters showing up - but web content in that font appears as intended.

Any clues?

Its more likely a problem with your set locale than with the fonts themselves.

Unfortunately,, although I will try my best, I don't really mess with my locales all too often since I use English exclusively.

in Arch Linux, the locales can be found in "/etc/locale.gen" but it could be different for your system.
In Ubuntu, I looked around and found them as well, in "/usr/lib/X11/locale/locale.alias" and "/etc/locale.alias"

If the file does exist, simply add the languages' corresponding locale and ISO and reboot.

You SHOULD be able to see your fonts as expected, but I can't give a guarantee because like I said, never tried to mess w/ that.

Hope this helps.