However, long term thinking I suppose there will be more demand for these categories in even more languages and they will clutter the menu and topic feed for the users who do not speak any of the added languages.
A possible solution to this would be to create groups for each supported language.
Create duplicates of each category for every language you want to support. And make them visible/writable only for members of the respective language.
Explain to your users that if they join any of these groups, they will be able to see the categories in the respective language.
Users can choose which languages they want to see (even multiple at the same time) by joining the respective language groups.
Enable “Allow user locale” in the settings to allow users choose the UI language they prefer (regardless of which groups they are in)
The only downside of this solution that I can see is that only the default language categories will be visible to people who are not logged in. In order to see the other ones, they have to log in and join the language group.