Adding languages to gedit spellchecker

I found an article that may be useful: https://help.gnome.org/users/gedit/stable/gedit-spellcheck.html.en

This states that you can Define the language to use for spell checking

By default, gedit will use your current language to spell check your document. If you need to use another language, choose Tools ▸ Set Language…, then choose the language you want to use.

EDIT: Sorry, I overlooked that a bit. I think you need to install dictionaries for them to show up in Tools > Set language menu I believe the languages will show up after you install the myspell-nl dictionary using System > Administration > Synaptic Package Manager

You can add a language, installing in your system the corresponding aspell library.

For instance, to install French language in Ubuntu, so that it appears in Gedit in the Tools → Set Language menu. Run this:

sudo apt-get install aspell-fr

(source)

After you do so, close Gedit and open it again