Same problem here, but in my humble opinion, it’s not systemd, but the latest update from ddcutil.
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Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-2 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-3 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-4 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-5 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-6 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-7 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-8 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-9 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-10 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-11 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-12 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-13 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-14 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-15 lacks R/W permissions
Feb 14 19:46:09 t14g5a org_kde_powerdevil[2369]: [ 2506] Device /dev/i2c-16 lacks R/W permissions
...
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: Failed to find connector name for /dev/i2c-10, set_connector_for_businfo_using_edid at line 1376 in file i2c_bus_core.c.
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2506] Adding connected display with bus 10
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2506] Emitting DDCA_Display_Status_Event[ 49.538: DDCA_EVENT_DISPLAY_CONNECTED, , dref: DDCA_Display_Ref[4], io_path:/dev/i2c-10, ddc working: false]
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2506] Starting 1 callback threads
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2506] libddcutil callback thread 0x7fe7980134b0 started
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2506] Started 1 event callback thread(s)
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2505] recheck thread terminating because watch thread terminated
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2505] Flushing request queue entry for Display_Ref[3:bus /dev/i2c-2 @0x7fe798028100]
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 3293] Invoking callback function 0x7fe7c5cb0110 for event DDCA_Display_Status_Event[ 49.538: DDCA_EVENT_DISPLAY_CONNECTED, , dref: DDCA_Display_Ref[4], io_p>
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 3293] Callback function 0x7fe7c5cb0110 for event DDCA_Display_Status_Event[ 49.538: DDCA_EVENT_DISPLAY_CONNECTED, , dref: DDCA_Display_Ref[4], io_path:/dev/>
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2369] Watch thread terminated.
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: Failed to find connector name for /dev/i2c-10, set_connector_for_businfo_using_edid at line 1376 in file i2c_bus_core.c.
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: Failed to find connector name for /dev/i2c-10, set_connector_for_businfo_using_edid at line 1376 in file i2c_bus_core.c.
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: EDID readable from /sys but not using I2C. Display change detection unreliable.
Feb 14 19:46:45 t14g5a org_kde_powerdevil[2369]: [ 2369] EDID readable from /sys but not using I2C. Display change detection unreliable.
...
I manually rolled back the two ddcutil packages to the Versions from 20260209
(https://download.opensuse.org/history/20260209/)
- libddcutil5-2.2.1-1.1.x86_64.rpm
- ddcutil-i2c-udev-rules-2.2.1-1.1.noarch.rpm
Since then, I have been able to log in again and there are no errors visible in the log.