the problem is that 'caja' the mate file manager needs to be launched in some sort of daemon mode so that it will manage the desktop icons and activate the desktop right-click menu

executing `caja --force-desktop` on a running system will achieve this and the dektop icons will be available as well as the right-click menu - but i suspect there is a configuration option for this somewhere that would control it globally and have the desktop launch in this mode by default