Power Options could not set the screen brightness on a real laptop (reported on a ThinkPad E14 Gen 5 running Linux Mint 21.3), and nothing that asks for a password through pkexec worked in the session. Two causes, both fixed:
- The backlight file belongs to root. The installer now writes a udev rule that hands it to the video group, applies it at once, and puts your account in the group, so Power Options sets the brightness straight from the file after your next logon. brightnessctl is installed as well, on every distribution.
- The session never started a PolicyKit authentication agent, so pkexec had nobody to ask and the brightness fallback, the lid and power-button settings, Device Manager's driver changes and Disk Management all failed at once. The session now starts whichever agent is installed (lxpolkit first), and the installer asks for one.
Where a laptop shows two backlights, the GPU's own is preferred over the firmware's, which often does nothing. The Power Options message says what to do when it still cannot.
After updating, log off and on once so the video group applies.
curl -sL jacktulli.github.io/w2k | sh