I have been using ChatGPT in assorted places.

So I wrote a ChatGPT for all the platforms I use it on (macOS, iOS and watchOS) that uses my OpenAI key, without using third party providers.

If you are interested, you can get the source and run it yourself on your devices here:

https://github.com/migueldeicaza/PlaticaBot

Or if you rather write your own, use my SwiftChatGPT library:

https://github.com/migueldeicaza/SwiftChatGPT