IMHO, M5-main has the best menu system around. I HATE the normal Gnome menu's, but MintMenu's are better than KDE's Kmenu or Tastymenu. But I can't install them in KDE. That is, Synaptic says they're installed but they won't run from command line, and I can't add it to the panel.
Tracking things down, I think the missing file is "liblaunchpad-integration0". ~integration1 is installed but it seems to not have all the qualities of its predecessor. I've noted that M5-Gnome has both ~0 and ~1 installed.
Can someone please point to where I can download it from Mint somewhere?