I updated Ubuntu-Mate 18.04 to 20.04 and all of my LibreOffice dialogs lost their title bar close button. This is a Mate thing. Gnome desktop continues to show the close button. A discussion from several years ago says that some version of Gnome decided to remove this button on dialogs that cannot be resized. Is there a config setting to bring this back? This is similar to but not the same issue as ordinary window title bar min/restore/close buttons.
