PowerDevil will not change screen brightness. Restarting the service fixes the issue for around 5 seconds, which then immediately ceases to work. Relevant journald snippet:
```
12/7/25 6:23 PM systemd Started dbus-:1.4-org.kde.powerdevil.discretegpuhelper@1.service.
12/7/25 6:23 PM systemd Started dbus-:1.4-org.kde.powerdevil.chargethresholdhelper@1.service.
12/7/25 6:23 PM systemd Started dbus-:1.4-org.kde.powerdevil.backlighthelper@1.service.
12/7/25 6:23 PM backlighthelper no kernel backlight interface found
12/7/25 6:23 PM org_kde_powerdevil Failed to register with host portal QDBusError(“org.freedesktop.portal.Error.Failed”, “Could not register app ID: App info not found for ‘org.kde.org_kde_powerdevil’”)
12/7/25 6:23 PM org_kde_powerdevil org.kde.powerdevil.chargethresholdhelper.getthreshold failed “Charge thresholds are not supported by the kernel for this hardware”
12/7/25 6:23 PM org_kde_powerdevil org.kde.powerdevil.backlighthelper.brightness failed
12/7/25 6:23 PM systemd Started Powerdevil.
12/7/25 6:23 PM kclockd PowerDevil found on DBus
12/7/25 6:23 PM plasmashell D-Bus service not available: “org.kde.ScreenBrightness”
12/7/25 6:23 PM org_kde_powerdevil Handle button events action could not check for screen configuration
12/7/25 6:23 PM kclockd Scheduled alarm wakeup at “Sun Dec 7 22:00:00 2025” .
12/7/25 6:23 PM org_kde_powerdevil org.kde.powerdevil.chargethresholdhelper.getthreshold failed “Charge thresholds are not supported by the kernel for this hardware”
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: “PHL 221V8LB” retrying to set DDC/CI brightness in 1000 milliseconds - attempt no. 1
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: “PHL 221V8LB” retrying to set DDC/CI brightness in 2000 milliseconds - attempt no. 2
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: “PHL 221V8LB” retrying to set DDC/CI brightness in 1000 milliseconds - attempt no. 1
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: “PHL 221V8LB” retrying to set DDC/CI brightness in 1000 milliseconds - attempt no. 1
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: “PHL 221V8LB” retrying to set DDC/CI brightness in 2000 milliseconds - attempt no. 2
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: “PHL 221V8LB” retrying to set DDC/CI brightness in 3000 milliseconds - attempt no. 3
12/7/25 6:23 PM systemd dbus-:1.4-org.kde.powerdevil.discretegpuhelper@1.service: Deactivated successfully.
12/7/25 6:23 PM systemd dbus-:1.4-org.kde.powerdevil.chargethresholdhelper@1.service: Deactivated successfully.
12/7/25 6:23 PM systemd dbus-:1.4-org.kde.powerdevil.backlighthelper@1.service: Deactivated successfully.
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
12/7/25 6:23 PM org_kde_powerdevil [DDCutilDisplay]: “PHL 221V8LB” failed to set DDC/CI brightness
12/7/25 6:23 PM org_kde_powerdevil Adjust screen brightness step failed: no displays available to adjust
```