Hello, I'm running Ubuntu Mate 22.04.1 LTS on my Lenovo Thinkpad x280 and I'm having issues with brightness control. If I use FN keys to set brightness, once rebooted the brightness is reset to what is in Power Management Preferences.
If I use xrandr or /sys/class/backlight/intel_backlight/brightness still the same, the brightness is reset to whatever is set in Power Management Preferences.
Basically, it doesn't matter what I do, the brightness settings are reset to whatever is set in Power Management Preferences -> Set display brightness to
I did changes to grub and whatever else, nothing changes. Please note that this wasn't happening on openSUSE with Xfce.