After latest update to 5.11.95, Discover appeared unbidden in Application Launcher Favorites section.
Right click on Discover, select Remove from Favorites, and it goes away... until the next time plasmashell is started or restarted.
Expected behavior: it really should not appear in Favorites unless selected. AND, it should not reappear after it has been removed!
*** This bug has been marked as a duplicate of bug 385814 ***