[vetinari]

Not correctly, though.

When talking about fractional scaling in Gnome, it is meant for all apps, not just GTK apps. Most apps do respect Xft.dpi, so they will scale their fonts, as the desktop environment sets it up, but not the other assets. Scaling all the other assets is the issue, not just the font rendering.

So yes, Qt apps in KDE do work correctly, (KDE is seting their QT_*_SCALE env variables). It does not work with GTK apps. Similarly, GTK apps do work correctly with fractional scaling in Gnome, but Qt apps do not, because Gnome doesn't set QT_AUTO_SCREEN_SCALE=0 and QT_SCREEN_SCALE_FACTORS like KDE does. Qt apps in Gnome look broken exactly like GTK apps look broken in KDE.

Proper fractional scaling means scaling all apps, not just apps made using single framework.