Using Linux Mint Cinnamon 18.3, the available version is 5.1.6.2 and I would like to upgrade to one of the current versions (5.4 “standard” or 6 “cutting edge”). How do I get my system to upgrade to newer versions?
Download and install the vanilla build from the official site.
Since you’re on Mint, you can make use of the Ubuntu PPAs.
You can follow the instructions on AskUbuntu, and it would be worth reading the full discussion there.
N.b. I don’t know whether you should purge your current installation if you’re going to use the PPA to install and maintain your LibO software. You could ask on the Linux Mint forums, or at Unix.Stackexchange – see, for example, this previous Q&A.
Essentially, you need to add the correct PPA to your software sources. See the official
“LibreOffice Packaging” team page for instructions on the different flavours and how to add the PPA. (Either “Fresh” or “Still” are main options, of course.)
Once you’ve done that, then in the terminal you can do:
sudo apt update
sudo apt install libreoffice
to install LibO to your system.