I have followed the fix found here: Backlight Issue
However I can't use the
sudo update-grub2 command as it errors with
/usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?)
As this laptop's hard drive is shot, I can't install the OS. So I'm using a live usb & I have been able to get it to temporarily work in Terminal with
sudo setpci -s 00:02.0 F4.B=00
I'm new to Ubuntu, so if you know how to fix this please provide as much detail to what I would need to do.