Changes made earlier don't revert after unticking its box and hitting apply. STEPS TO REPRODUCE 1. Open System Settings 2. Go to Power Management 3. Tick Change screen brightness and adjust it to a noticeable amount, hit Apply 4. Untick Change screen brightness, hit Apply OBSERVED RESULT The brightness doesn't revert. EXPECTED RESULT The brightness should revert to the default amount. SOFTWARE/OS VERSIONS kinfo output: Operating System: Alpine Linux 3.23.2 KDE Plasma Version: 6.5.4 KDE Frameworks Version: 6.19.0 Qt Version: 6.10.1 Kernel Version: 6.18.1-0-lts (64-bit) Graphics Platform: Wayland Processors: 4 × Intel® Core™ i7-7600U CPU @ 2.80GHz Memory: 15.5 GiB of usable RAM Graphics Processor 1: Mesa Intel® HD Graphics 620 Graphics Processor 2: NV118 ADDITIONAL INFORMATION I don't think this only happens with this specific tickbox, should also present elsewhere (not with just this setting).
That's because this isn't a conventional brightness slider; it's a setting to determine what brightness level will be applied *automatically* when the system is in the specified power state. If you disable that feature, you're telling it "don't automatically adjust the brightness to such-and-such level anymore", which is to say, keep it at the same level. Which it does.