opensuse/arch sddm hidpi

 /etc/sddm.conf.d/hidpi.conf

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

[Wayland]
EnableHiDPI=true

[X11]
EnableHiDPI=true
ServerArguments=-nolisten tcp -dpi 192 

 ref: forums.opensuse.org