When LibreOffice is installed it comes with the English dictionary pre-installed (on a English installation). If you need a dictionary for a language other than English, follow this article.
First we need to find the right package name. Open a terminal window and run:
apt-cache search myspell
This will list several
myspell packages and in front of the name of the package a description will tell which language the package is for. Annotate the
myspell package name.
sudo apt-get install MYSPELL_PACKAGE to install the package (replace
MYSPELL_PACKAGE with the name determined before). Example for European Portuguese:
sudo apt-get install myspell-pt-pt