What about https://huggingface.co/chat/ ? Seemed to work well prompting it to translate, can you download the model and do it locally somehow? Open source chat gpt. 
Discussion
You could totally wrap a LibreTranslate API around huggingface models , there’s just a question of hosting costs. It’s probably going to be cheaper to pay for a service than host yourself, because the best models, like NLLB for example are going to be super expensive, hundreds of USD or more per month, depending on which model size you build. I’m hoping to add more models like that to nokyctranslate, but hosting costs mean we have to wait until we reach a certain number of users.