Comment # 1 on bug 1054071 from Michal Srb

The new thing in Tumbleweed is fontconfig 2.7 which brings version 40 of the
hinting engine. Version 40 is trying to look more like ClearType on Windows and
it ignores horizontal hinting, see here:
https://www.freetype.org/freetype2/docs/subpixel-hinting.html

The results look more or less acceptable if antialiasing is enabled, but
without antialiasing they look pretty bad - like if no hinting was enabled. So
if you disable antialiasing you may also want to switch to version 35. It can
be done by setting environmental variable:
FREETYPE_PROPERTIES="truetype:interpreter-version=35"

It would be great if it could be done using a fontconfig configuration, but
AFAIK it is not possible yet. In my personal opinion, it would be best to keep
using 35 by default, but that means going against upstream and we would need
some community agreement on it.

However, the fact that some applications look fine on your system and ftview
shows "engine: v35" on your screenshot makes me think that you already found
about this variable and set it, but for some reason it does not work in all
applications.

Can you share your font configuration? Any changes you did in
/etc/fonts/conf.d, ~/.fonts.conf, .fonts.conf.d, environmental variables, etc.