If I switch my setting for SDDM to use a plasma-bigscreen session, it just runs the bigscreen-plasma load animation, then loads a black screen with a cursor. I can use ALT-F2 to search and launch programs but the interface never actually appears. I've tried creating a new user with a clean Plasma profile and get the same behavior with that user. I get a popup dialog with the error: "Expression failed: BZ_IS_BACKEND (self)" when I open the searchbar.