The primary method for setting the global and text scale for GTK applications is by using the
gdk-unscaled-dpi settings. Those are also read by GTK4, which at the same time dropped usage of GDK_DPI_SCALE.
Note that the scaling settings are only relevant on X11; On Wayland the DPI scale is communicated directly by KWin to applications on a per-monitor basis.
See also kde-gtk-config!49 (merged)
CCBUG: 442901 FIXED-IN: 5.27