You're quite right. With enough fiddling around and installing LibreOffice instead, I got a more useful error:
The application cannot be started. LibreOffice user installation could not be processed due to missing access rights. Please make sure that you have sufficient access rights for the following location and restart LibreOffice: /home/julius/.config/.libreoffice/3
The only thing that confused me was that the folder was hiding in .config/ rather than directly in the home directory, like it was in the other threads. The question is: what should the permissions be? If I do the "user profile reset" procedure it chokes while generating a new profile, saying:
Either another instance of LibreOffice is accessing your personal settings or your personal settings are locked. Simultaneous access can lead to inconsistencies in your personal settings. Before continuing, you should make sure user 'root' closes LibreOffice on host 't-newlaptop'. Do you really want to continue?
I don't really know what it means by that. I was not currently logged in as root (I ran 'libreoffice' as my user) and 'ps aux' did not turn up any currently running LibreOffice or OpenOffice processes. I think that the error is appearing simply because, for whatever reason, it cannot write to my home directory.