How to uninstall LibreOffice?

Type the following in terminal to remove libreoffice:

sudo apt-get remove --purge libreoffice*
sudo apt-get clean
sudo apt-get autoremove

An especially thorough removal technique.

Suitable generally, but especially when removing LibreOffice to replace it with a manually installed LibreOffice or OpenOffice.

Assuming LibreOffice is provided by official Ubuntu packages on your system (which it generally is, unless you've installed it yourself from other packages or from the LibreOffice website), you can thoroughly remove it in the Terminal:

sudo apt-get remove fonts-opensymbol libreoffice libreoffice-\* openoffice.org-dtd-officedocument1.0 python\*-uno uno-libs3-\* ure ure-dbg

If you want to remove global configuration files too (this does not affect per-user configuration in users' home directories), replace remove with purge.

I think it's unlikely that removing any of this will break other programs, because Lubuntu doesn't come with LibreOffice, and Lubuntu users are able to run just about any Ubuntu program, without having to install LibreOffice.

Still, that is a legitimate concern and I cannot guarantee that nothing depends on your existing LibreOffice installation. Fortunately, the most serious breakages can be averted by making sure that nothing you need is removed with the LibreOffice packages. You can either be very careful while running the removal command (watch out for whatever else it says will be uninstalled), or simulate the removal first:

apt-get -s remove fonts-opensymbol libreoffice libreoffice-\* openoffice.org-dtd-officedocument1.0 python\*-uno uno-libs3-\* ure ure-dbg

(That is, put -s right after apt-get, and, optionally, remove the sudo.)

I haven't heard about any problems arising from removing fonts-opensymbol but those are fonts, and not enough people remove the package to know if problems viewing documents are common. So if the simulation reveals that a number of other packages you need or are unfamiliar with would be removed, try simulating without removing fonts-opensymbol and see what happens. And you might decide just not to remove that one at all.

The above technique uninstalls all LibreOffice packages provided in Ubuntu. I got the list of packages from here.

To shorten the command and avoiding having to type the name of every individual package, and also potentially to extend the life of this procedure in case differently named packages are provided in later versions of LibreOffice, I used the * wildcard to cover many packages at once. It is itself escaped with \ so that it won't be expanded by the shell into the name of some unrelated file or directory, before it is passed on to apt-get.

_{Related: How to replace LibreOffice with OpenOffice?}

As a corollary, you can use aptitude to search for which packages to uninstall:

aptitude search '~i' | grep libreoffice

which returns a list of all installed packages that contain the text 'libreoffice'. Grep is neat!

Then use apt-get to remove the main package that you have installed, and apt-get autoremove will remove all the smaller packages which are no longer necessary. Hope that piece of advice helps!