SUMMARY
"Turn off screen" in "Power managerment" is set to 1 min.
"Lock screen automatically" in "Screen Locking" is set to 1 minute too.


STEPS TO REPRODUCE
1. Bootup and do nothing for 2 minute. 

OBSERVED RESULT
The screen is kept on always.

EXPECTED RESULT
The timeout of screen off can work.

SOFTWARE/OS VERSIONS
Distro OS: Fedora 40/41.
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 6.1.90
KDE Plasma Version: 6.1.90
powerdevil version: 6.1.90-1.fc41.x86_64

ADDITIONAL INFORMATION
$ xset q
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:
  catalogue:/etc/X11/fontpath.d,built-ins
DPMS (Display Power Management Signaling):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Enabled
  Monitor is On

All of the kde and plasma config files in .config had been removed.
Neither fedora 40 plasma 6.1.5 or fedora plasma 6.1.90 can work.