What fonts do I need to install on Ubuntu in order to see special characters (💋 for example)?
Well apparently this was a "fonts" problem for specific languages.
Visit this Wikipedia page: List of ISO 639-1 codes and check the languages that aren't working for you.
I had the same issue for the Tibetan language which were showing those squares instead of the actual character. Installing the package
So in order to fix the other languages, you need to install the necessary font package for that language.