Plasma Login Manager not allowing monitors to go into power save mode

[oshunluvr]

Under SDDM, the monitors will go into sleep mode as expected.

Using Plasma Login Manager, the login screens stay on indefinitely.

[Snowhog]

Provided ONLY because something within may spark an inquiry into the right direction.

AI Overview

If your Plasma login manager or screen locker is staying on indefinitely instead of turning off the monitor or going to sleep, it is usually caused by a conflict between KDE's screen locking settings, the Display Manager (SDDM or Plasma Login Manager), or systemd idle actions.
Here is how to troubleshoot and resolve the issue:

1. Configure Systemd for Pre-Login Idle Sleep

KDE's login screen (SDDM or the new Plasma Login Manager) relies on systemd to turn off displays or suspend the computer before a user logs in. If it's staying awake, you may need to define the idle action manually:

• Open your terminal.

• Edit the logind configuration file using a text editor like nano: sudo nano /etc/systemd/logind.conf

• Scroll down and find the [Login] section. Ensure these lines are uncommented (remove the # if present) and set to your preferred values: ini
  
  
  [Login] IdleAction=suspend IdleActionSec=10min
  
  Use code with caution.

• Save and exit (in nano, press Ctrl+O, Enter, then Ctrl+X).

• Restart the systemd-logind service to apply changes: sudo systemctl restart systemd-logind

2. Adjust Screen Locking Settings

If the issue occurs after waking from sleep or when the lock screen activates while your session is active, you can adjust the lock screen's timeout behavior:

• Open System Settings.

• Go to Workspace Behavior -> Screen Locking.

• Make sure Lock screen automatically is checked and set to a specific time (e.g., 5 or 10 minutes).

• Click Apply.

3. Check for Theme or Display Manager Glitches

Sometimes, specific SDDM themes (like the default Breeze theme) can cause the login screen to hang or fail to turn off the display.

• Open System Settings -> Colors & Themes -> Login Screen (SDDM).

• Click the image icon on a different theme (or a different style) to switch it.

• Click Apply.

• If you are using the newer Plasma Login Manager and are experiencing freezing, you can switch back to SDDM by running: sudo systemctl disable plasmalogin and sudo systemctl enable sddm, then rebooting.

[claydoh]

https://bugs.kde.org/show_bug.cgi?id=513159

This may still be relevant.

I can't remember if this was broken or non-functional before, as I mostly use autologin. I have been using PLM otherwise for at least a month or two before it was made the default. I only noticed the lack of screen timeout when autologin was broken in PLM circa the 6.7.0 release. That part works now.

[oshunluvr]

https://bugs.kde.org/show_bug.cgi?id=513159

This may still be relevant.

I can't remember if this was broken or non-functional before, as I mostly use autologin. I have been using PLM otherwise for at least a month or two before it was made the default. I only noticed the lack of screen timeout when autologin was broken in PLM circa the 6.7.0 release. That part works now.

That bug report seems relevant. I have plasmalogin 6.7.3-0zneon+24.04+noble+release+build23 and do not use autologin. I really don't want to have my monitors on all night as I usually leave this PC on 24/7

Still using SDDM on Kubuntu as plasmalogin isn't available there yet AFAIK.

[claydoh]

Luckily you can install and switch to SDDM.

I keep forgetting to test PLM and see in there is something that might fix or work around this.

I really don't want to have my monitors on all night as I usually leave this PC on 24/7

This is also happening on your lock screen, or are you logging out from the desktop at the end of the day?