Keyboard layout for the GNOME session can be selected in GDM, however it is not mandatory. If you do not select any keyboard layout, the default keyboard layout is selected. You can select a different layout later in the GNOME session or the next time you log in.
The "Keyboard Layout Selection" panel becomes visible. This panel is located at the bottom of the GDM window, as shown in the following figure.
The default value of the keyboard layout is set to USA.
A window containing a list of all the available keyboard layout variants appears as shown in the following figure.
If a keyboard layout is selected in GDM, the value of the selected keyboard layout is stored in the file $HOME/.dmrc and it will be preselected on the next login.