I have been told recently by Nvidia's Aaron Plattner that the long-standing problem "brightness control not working" has finally been solved by introducing the new "nvidia.NVreg_EnableBacklightHandler=1" option.
And after applying the following suggestion, brightness control really works on my Asus G752VS laptop (Nvidia GTX 1070):
$ sudo su $ mkdir -p /etc/kernel $ echo "nvidia.NVreg_EnableBacklightHandler=1" > /etc/kernel/cmdline $ clr-boot-manager update $ exit
Aaron also said that the mentioned option will be enabled by default in a future release. Ater updating my Solus this morning, this si still not the case. Without adding kernel parameter "nvidia.NVreg_EnableBacklightHandler=1" - brightness control is not working.
Even if in some way we can say that the brightness control somehow works now, both by using the slider within Pover options and by using the keyboard FN keys, the reality is that it doesn't work ok. Current long-standing situation is that Solus still keeps resetting brightness to maximal 100% on every restart.
Aaron Plattner:
"Remembering and restoring the backlight brightness on restart isn't the driver's job, it's the desktop environment's (or maybe systemd-backlight@.service's, I guess?)"