Addon in questions are Adapta Theme, AlphaBlack Widget.
Please see https://community.kde.org/Get_Involved/Bug_Reporting. If Discover is hanging or crashing, we need a backtrace. See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports
It's impossible to uninstall things from kde store. I have just tried to uninstall adapta kde theme and some widgets (event calendar, present windows button). Uninstall process hangs (adapta theme) or discover pretends to uninstall correctly but the widget remains on the system.
(In reply to Dr. Chapatin from comment #2) > It's impossible to uninstall things from kde store. > I have just tried to uninstall adapta kde theme and some widgets (event > calendar, present windows button). Uninstall process hangs (adapta theme) or > discover pretends to uninstall correctly but the widget remains on the > system. I forgot to say: Discover 5.14 beta on Arch Linux.
*** This bug has been marked as a duplicate of bug 397257 ***