Add to boot optins to control bightness. For disable control for amd gpu
kernelstub -a amdgpu.backlight=0
Nvidia driver bug with backlight. You may install 460 driver, but it doesn't work with new kernel 5.13+(?) https://forums.developer.nvidia.com/t/laptop-backlight-control-regression-with-465-24-02/175585/48 Temporary solution for backlight
xrandr --output DP-4 --brightness 0.5
First of all you need kernel at least 5.15.5-76051505-generic (?)
be sure to enable freesync BEFORE XRANDR, to enable freesync create /etc/X11/xorg.conf.d/20-amdgpu.conf (!) Note what second monitor may be turn off because of amdgpu and mux switch
Section "Monitor"
Identifier "eDP"
Modeline "2560x1600_165.00" 777.340 2560 2608 2640 2720 1600 1603 1609 1732 -hsync -vsync
Option "PreferredMode" "2560x1600_165.00"
EndSection
Section "Device"
Identifier "AMD"
Driver "amdgpu"
Option "VariableRefresh" "true"
Option "TearFree" "1"
Option "DRI" "3"
EndSection
Then
xrandr --newmode "2560x1600_165.00" 777.340 2560 2608 2640 2720 1600 1603 1609 1732 -hsync -vsync
xrandr --addmode eDP "2560x1600_165.00"
xrandr --output eDP --mode 2560x1600_165.00
If you have troubles with WIFI or bluetooth, so Create a file named /etc/module.d/50-rtw89.conf. In this file, create a line that says
options rtw89pci disable_aspm_l1=y
and reload modlue
sudo modprobe -rv rtw89pci
sudo modprobe -v rtw89pci