I had this problem before, but with the new KDE updates, it might have broken something.
I have it set to switch off my monitors after 20 minutes of inactivity. If I watch a movie and fall asleep, when the movie is done, it will turn off my screens after 20 minutes of it ending. But since 2 weeks ago, this isn’t happening.
As seen here. Is there some other location which is overpowering this? I used to have “suspend session” selected, too. And had problems, but after I unchecked that, it worked OK.
I don’t know much about it so won’t be much help, but you could check your current DPMS settings with xset q then see if you can manually blank it with
xset dpms force off (Turn off screen immediately)
xset dpms force standby (Standby screen)
xset dpms force suspend (Suspend screen)
More on DPMS can be found here: https://wiki.archlinux.org/title/Display_Power_Management_Signaling
If triggering it manually works, you’ll have at least narrowed it down to an issue with KDE and then you can start checking it’s logs and forums if no one else here has any ideas
** edit ** I’ve seen several older posts on the net saying kscreen has caused issues in the past so that could be something to explore as well
Keyboard Control:
auto repeat: on key click percent: 0 LED mask: 00000002
XKB indicators:
00: Caps Lock: off 01: Num Lock: on 02: Scroll Lock: off
03: Compose: off 04: Kana: off 05: Sleep: off
06: Suspend: off 07: Mute: off 08: Misc: off
09: Mail: off 10: Charging: off 11: Shift Lock: off
12: Group 2: off 13: Mouse Keys: off
auto repeat delay: 600 repeat rate: 25
auto repeating keys: 00ffffffdffffbbf
fadfffefffedffff
9fffffffffffffff
fff7ffffffffffff
bell percent: 50 bell pitch: 400 bell duration: 100
Pointer Control:
acceleration: 2/1 threshold: 4
Screen Saver:
prefer blanking: yes allow exposures: yes
timeout: 0 cycle: 600
Colors:
default colormap: 0x20 BlackPixel: 0x0 WhitePixel: 0xffffff
Font Path:
built-ins
DPMS (Display Power Management Signaling):
Standby: 0 Suspend: 0 Off: 0
DPMS is Disabled
Why try only one mode? I’m not sure what the difference is between standby, suspend, and off when it comes to display power mangement and how they’re all activated. I’d try setting all three. Also, it looks like you don’t have a timeout for any blanking either. Set that with xset s 300 or whatever.
If that doesn’t work maybe someone else can help. It’s possible whatever KDE is using is overriding xset and I’m not too familiar with KDE power management.