Setting fonts dpi doesn't affect qt5 apps, like pcmanfm-qt or qt4wine. OS: Arch Linux.
The culprit is qt5 apps not understanding the font format in "~/.config/kdeglobals". If I run: pcmanfm-qt I get: QFont::fromString: Invalid description 'Noto Sans,11,-1,5,400,0,0,0,0,0,0,0,0,0,0,1' QFont::fromString: Invalid description 'Hack,11,-1,5,400,0,0,0,0,0,0,0,0,0,0,1' QFont::fromString: Invalid description 'Noto Sans,11,-1,5,400,0,0,0,0,0,0,0,0,0,0,1' QFont::fromString: Invalid description 'Noto Sans,11,-1,5,400,0,0,0,0,0,0,0,0,0,0,1' But if in kdeglobals I change: font=Noto Sans,11,-1,5,400,0,0,0,0,0,0,0,0,0,0,1 To: font=Noto Sans,11 Both qt5 and qt6 apps shows the correct font size. So if that is a new qt6 format, maybe we should delay that a little bit. Till more apps use qt6. For example pcmanfm-qt will upgrade to qt6 at the end of April: https://github.com/lxqt/pcmanfm-qt/commit/adf83ac373cd826c1ac16ad9702c04de8f757f8c
Is plasma5-integration installed?
Installing the packages mentioned here: https://discuss.kde.org/t/how-to-set-qt5-font-size/11820/7?u=albertosalvianovella Solved the issue, so I guess this isn't a bug.