Does tribe support multiple languages at the same time? Or would I have to creat one community (with an individual domain) per language?

Yes, this is one of the advantages on Tribe that you as an admin can change the default language for the entire community. This is available on all plans. You can learn more here16. 

Also, if you are on a Premium or Enterprise plan, your community users can change their preferred language from their account settings. You can learn more about this feature here18.