I'm running the Openbox session of Lubuntu. The Lubuntu dev has made something called lxclipboard and that works even in an Openbox session. It's very elementary but I don't need a sophisticated clipboard manager. My next choice, again keeping minimal resources and dependencies in mind,would be xfce4-clipman. The one pita is LibreOffice. If I copy something and assume it's in the clipboard and close LibreOffice before pasting the stuff elsewhere, it's gone. IIRC, the LibreOffice devs are aware of the issue but regard it as a feature.