I've managed to get the backlight working roughly as well! All I needed to do was to load msi-laptop with the parameter force=1. The problem is that there is so far very little scaling, I can only set brightness to 0 (very dark) or 1-8 (all "very bright"). Check for updates to get it working well with KDE.
I've contacted the driver developers and I hope we can make some progress on the drivers soon.