When background is changed in SDDM KCM it saves the settings but nothing is changed. SDDM doesn't have access to files in a user's home folder. Background must be saved somewhere it is available to be accessed by SDDM. Reproducible: Always Steps to Reproduce: 1.System Settings > Startup and Shutdown > Login Screen > Background 2. Change background 3. Reboot Actual Results: Background change fails if background image is in home folder. User is not notified. Further details and suggestions can be found in the sddm github issue https://github.com/sddm/sddm/issues/350
Same thing here, SDDM does not save settings and changes to the background.
*** This bug has been marked as a duplicate of bug 344867 ***