Open Application Menu's config dialog, the shortcut is Alt+F1 by default, if set to that it activated the menu when the Super/Win key is pressed. - set the shortcut to something else, press Super/Win the menu is still activated - unset the shortcut altogether, press Super/Win the menu is still activated Editing ~/.config/kwinrc and adding: [ModifierOnlyShortcuts] Meta= stops the Super/Win key from activating the menu.
This was an intentional change that was made to fix many bugs; see https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/1937. Your workaround is in fact now the expected method of manually disabling it. :)