It’s been 2 years that I bought my current laptop: a Asus UX32LA. After a year on Windows, I decided
to pass it on Linux. I’m currently using Arch Linux but I had a screen backlight fn keys issue
with others distributions too (mainly Ubuntu and Fedora). The fix is very simple but not
straightforward to find. You just have to put
acpi_osi= in your kernel boot option.
This option disables all strings from the
acpi_osi arguments. This arguments changes the list
of supported OS interfaces for the BIOS. I hope this help!