Yes, there are dictionaries for a multitude of languages. But (other than the base British English dictionary and USA dialect of GUI language) added dictionaries and languages are optional during installation.
Click on the screen capture below to read an interesting discussion about dictionary selection.
There is a wiki page about troubleshooting the spellcheck. But it is from before Gramps changed spelling systems. So that webpage is likely to have directions that are outdated.
https://www.gramps-project.org/wiki/index.php/Troubleshoot_Spellcheck