FWIW I just put Windows onto a ROG GX531GX to gift it to a family member, (I told him it was a testament of my love that I was going from Linux TO Windows on a system for the first time ever) but have been gaming on it under Linux for a couple of years, and under KDE plasma was a slider for the keyboard backlight with the power settings, which required no extra attention from me (that I can recall) to get there.
I may have had to install an "asus laptop" or similar labeled package from my package manager and forgotten about it, but it was for sure no more than that or I'd have remembered.
Edit: I'm posting this from a different computer but it was likely one of these.