KDE Plasma 6 SDDM HiDPI FIX

sudo nano /etc/sddm.conf.d/hidpi.conf

[Wayland]
EnableHiDPI=true

[X11]
EnableHiDPI=true

[General]
GreeterEnvironment=QT_SCREEN_SCALE_FACTORS=2,QT_FONT_DPI=192

Источник: https://wiki.archlinux.org/title/SDDM#Enable_HiDPI