There seems to be a conflict in gemian v4 with LibreOffice. Attempting to install LibreOffice gives a warning that it will remove packages camera-app. media-hub, messaging-app. I recall that the message app disappeared on installing LibreOffice in gemian V3, which could be fixed by re-installing the message app. I aborted the installation of LibreOffice this time, but presumably the next thing to try is re-installing these packages after LibreOffice.