I've been using Univerbal happily with Italian. Dutch is one of its 20 languages. Worth noting that it's a paid app but seems to have a lot of polish. I found out about it on HN so I'm sure you can look up discussions to get more opinions on it (though it's quite frequently updated).
I'm really impressed by this app. it's not just a chat. GPT wrapper. I wonder if on device models are good enough for these tasks. this could cut the cost significantly instead of using openai API, for example
The fact that the Dutch translation of the app is awful does not inspire confidence. Really basic stuff like translating "No" to "Geen" (none) in a yes/no question
https://www.univerbal.app