Ask HN: AI approaches to learning and practicing language?

I've been interested in learning and being exposed to many languages as a hobby, and it seems to me that LLMs are an extremely good fit as a tutor, especially for high-resource languages.

Are there language learning platforms, or projects, that have, say, conversing with an AI in various scenarios or writing in a particular register as the primary mode of instruction (or as the core product)?

Alternatively, what are your experiences with using general purpose LLMs for such a task, and what would you suggest to optimize for fun and learning? E.g. maintaining a basket of scenarios, prompts to ask the AI to reword something in how a native speaker would express it, drilling down or translating something you don't understand.