As a workaround, run Freeciv with AppMenu (global menu) disabled. Type in the terminal: "UBUNTU_MENUPROXY= freeciv" (no quotes and a whitespace after '='). So the bug is some kind of incompatibility with AppMenu.
As a workaround, run Freeciv with AppMenu (global menu) disabled. Type in the terminal: "UBUNTU_MENUPROXY= freeciv" (no quotes and a whitespace after '='). So the bug is some kind of incompatibility with AppMenu.