I just found a strange thing under Linux and would be happy if one or the other Linux user could have a look at it to exclude or verify a bug.
If you switch off “Supports Hi-DPI” in Xojo Build Settings and draw on the Graphics context, Graphics.ScaleX/ScaleY still have the value 2 (Hi-DPI), which should be 1 (LowRes).
I would not consider this a bug since the OS does not provide any kind of virtual scaling for “LowRes” apps like Windows and macOS do. You could however force your app to not scale, but I don’t think that’s quite the same: export GDK_SCALE=0.5 GDK_DPI_SCALE=0.5; ./MyApplication
Type that in a Terminal session to see the affect, it just sets up some environment variables. You may also be able to setup those environment variables in Xojo code, but depending on how they are used by X11/Wayland/GTK+ it may need to be setup earlier then we get the chance to.