It's not exactly what OP wants out-of-the-box, but if anyone is considering building one I suggest taking a look at this.¹ It is really easy to tinker with, can run both on devide or in a client-server model.
It has the required speech-to-text and text-to-speech endpoints, with multiple options for each built-in. If you can make the LLM AI assistant part of the pipeline to perform translation to a degree you're comfortable with, this could be a solution.
¹ https://github.com/huggingface/speech-to-speech