When using monteverdi from Debian unstable I found out you need to set the environment variable OTB_APPLICATION_PATH to /usr/lib/x86_64-linux-gnu/otb/applications should this be somehow preset in the debian install, or in a README.Debian?
I did find that /usr/share/applications/monteverdi.desktop does include this, but that doesn't help users who launch applications from the command line.