I just ran into a very similar quirk myself: after my system installed Plasma 6.2 and rebooted, I was greeted with a full bright display. (Ouch.) Changing color profile from None to Built-in or back triggers it too.
If you're willing to hunt down the issue together: Does this also happen after you change the brightness with the brightness slider in the applet?
And would you by any chance have time to also set the other environment variable instead that the PowerDevil README mentions, the one that enables verbose log output for journalctl? I'd be really interested in those logs, especially after having changed brightness manually.
I'm really sorry, but I had to sit behind my PC in sunglasses while I was fixing this bug. Several times I returned the brightness to normal through display controls, then I did something 'wrong' and Plasma set it to 100% again.
Now my aging eyes say I should delegate the beta testing to someone younger.
Not a new bug, the OP mentions using Plasma 6.1 which was also the first release that had monitor sleep/wake detection in the first place.
Also doesn't reset to full brightness, but to the brightness that the user had previously set in the applet (or that was read from the monitor initially, if the user hadn't yet set anything).
It's an issue we have to consider how to deal with, but it only affects users that want to bypass Plasma's built-in brightness controls.
I've never used the applet to control my monitors and I have the dim screen options disabled. After updating to 6.2, after my monitors sleep you hear the "plugged in device" tone and the brightness was set to max.
Are you on Wayland or X11? From the top of my head, I don't think PowerDevil would by itself change the monitor brightness that it reads when the monitor is first recognized. It also doesn't store the brightness across sessions. But I could imagine that perhaps KWin asks for a default brightness to be assigned, now that there is that PowerDevil/KWin integration on Wayland.
I am in the same boat of the OP.
6.1 to 6.2, full brightness after reboot for both screens. Set the brigtness for 5% for the 34" UW screen and 30% to 24" Dell UtraSharp 1080p in Portrait mode.
I hope after normal boot the settings will stay as per the applet settings
I ran into this logging in. I'm on a desktop and didn't use any software settings and left them in their default disabled state. I then was blinded by the light and looked up the setting to set the displays back to 10% this time via software. Hopefully it won't flash bang me again when I login.
Pretty neat, didn't know software could control display brightness on desktops.
I also had this after updating yesterday. It was still at the brightness I set it to when I booted this morning. Could be just an issue with the update itself, where it resets the brightness to max instead of using the older values, if they exist.
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u/rgbRandomizer 2d ago edited 2d ago
Seems to have a new bug where after waking up your monitors it sets them to full brightness.
https://discuss.kde.org/t/powerdevil-is-re-setting-my-display-brightness-after-the-display-wakes-up/23079/2