Here it is not possible to run VLC from Firefox as the
/usr/share/applications/vlc.desktop file is missing: it is currently
provided by the vlc binary package, while it should have been provided
by a package installed with the executable (or perhaps vlc-data).

Note: The reason I no longer install the vlc package on this machine
is that it installs too much, in particular a plugin that breaks the
system via dependencies.