this works to keep the keyboard lighting ON / keeps if from defaulting to OFF after 30 seconds....
thanks to user "
Harsh3338" who wrote in Dec 2019: Not sure if this is a late post, but let me put it out there.
I am using Nitro 5 AN515-43, and found a solution for the Keyboard back light.
-> Open NitroSense application (default app for Fan control), if you don't have it please download from the Acer website & install the latest version, if it is supported for your machine.
-> Go to Settings (Click on the gear icon you find on top right corner).
-> You will find Keyboard Setting there, just below that "Backlight off after 30 Seconds" -> just Disable this option and you are good to go.
-> To increase the backlight brightness press Fn + F10
-> To decrease the backlight brightness press Fn + F9
-> You're Welcome :-)
https://community.acer.com/en/post/quote/573425/Comment_765870