See if this link works better. Search results for 'Backlight in:title' - Zorin Forum
Basically, use the Search feature and paste Backlight in:title in it to search only in titles. 2 of the 5 results are:
How to Enable Keyboard Backlight Function Key Combinations (Zorin 15.3)
&
Keyboard backlight not working
There are two others I’ll not listing. They’re unsolved but may have useful info for you.