Can you please install evtest, run sudo evtest in a terminal, choose
the right device (Dell extra keys, or just the standard keyboard),
press these two keys, and copypaste the output? Use Control-C to stop.
Please also run udevadm info --export-db /tmp/udev.txt and attach
/tmp/udev.txt here.
$ sudo evtest
No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0: Power Button
/dev/input/event1: Sleep Button
/dev/input/event2: Lid Switch
/dev/input/event3: Power Button
/dev/input/event4: AT Translated Set 2 keyboard
Thanks. Your attached udev.txt confirms that the keymap matching worked:
P: /devices/platform/i8042/serio0/input/input4/event4
[...]
E: KEYBOARD_KEY_85=brightnessdown
E: KEYBOARD_KEY_86=brightnessup
[...]
and your evdev output on event10 confirms that the device *claims* to
support
