GPT-4 is actually quite good with languages. You can even get it to do some local Dutch dialects. We use it (via the code gpt plugin) for helping us with localization files for apps. We just give it whole chunks of localization files (mozilla fluent) and task it with translating those while preserving the id structure. Aside from minor formatting issues, I've not caught it making any mistakes. I doubt we'll be working with external contractors for localizations again.

It's also really good at doing things like synonyms. We used this to improve our icon search by letting it come up with comma separated lists of alternatives for each icon name. Worked really well too.

And it can do fictional languages. We did a pirate speak localization a few weeks ago for international pirate day. Just for giggles but it works.