STEPS TO REPRODUCE 1. open SDDM KCM 2. click on the button to set a custom background to Breeze SDDM theme 3. click on 'Load from file...' button and choose a file from your file system 4. click on 'Apply' button and enter your password to confirm the change OBSERVED RESULT the preview of Breeze theme is still showing the default background instead of the one applied in the last step. If we reopen the SDDM KCM and then click on the button to set a custom background again, the 'Change background' popup also shows the default background. EXPECTED RESULT The preview and 'Change background' popup of SDDM themes should always show the background currently in use SOFTWARE/OS VERSIONS Operating System: KDE neon Unstable Edition KDE Plasma Version: 5.25.80 KDE Frameworks Version: 5.95.0 Qt Version: 5.15.4 Graphics Platform: Wayland
Unfortunately the theme preview can't show the actual wallpaper since it's a static image set by the theme creator. The wallpaper chooser sheet shows the actual wallpaper though. I cannot reproduce the issue you're seeing of it always showing the default image.
Yesterday I changed the SDDM background and was unable to reproduce. Today the popup to change the SDDM background is unexpectedly showing the default SDDM background. Operating System: Arch Linux KDE Plasma Version: 5.25.0 KDE Frameworks Version: 5.95.0 Qt Version: 5.15.4 Graphics Platform: Wayland
*** Bug 460424 has been marked as a duplicate of this bug. ***
*** This bug has been marked as a duplicate of bug 436272 ***