Ola Junior,
Seguem os dados:
:~$ ls -al /dev/input/by-path/
[...]
lrwxrwxrwx 1 root root 9 Jan 21 07:39 platform-i8042-serio-0-event-kbd -> ../event0
:~$ cat /etc/gdm/gdm.conf
[...]
[server-Xephyr2]
name=Xephyr2
command=/usr/local/bin/load_Xephyr -display :0.1 -xauthority /var/lib/gdm/:0.Xauth -fullscreen -keybd evdev,,device=/dev/input/by-path/platform-i8042-serio 0-event-kbd,xkblayout=br,xkbmodel=abnt2 -mouse evdev,,device=/dev/input/by-path/pci-0000:00:1d.2-usb-0:2:1.0-event-mouse -mouse evdev -dpi 96
handled=true
flexible=false
[...]
Eu coloquei esses dados no daemon.conf do gdm3 e nao rolou.
Abracao