I am still seeing this or a related bug. With gnome-shell 3.28.1-3.fc28 installed, every text I type is using the english (US) keyboard layout in gdm, no matter what keyboard layout I configured. Switching the layout at runtime does not change anything. I have 3 layouts configured (de: neo, de: nodeadkeys, us). GDM always uses the last one no matter which one I configure.
On any tty and within any Gnome session, keyboard layouts behave correctly, using the default de:neo keyboard layout.
I am still seeing this or a related bug. With gnome-shell 3.28.1-3.fc28 installed, every text I type is using the english (US) keyboard layout in gdm, no matter what keyboard layout I configured. Switching the layout at runtime does not change anything. I have 3 layouts configured (de: neo, de: nodeadkeys, us). GDM always uses the last one no matter which one I configure.
On any tty and within any Gnome session, keyboard layouts behave correctly, using the default de:neo keyboard layout.
This looks like bug #1573923 to me.