What are some small LLM models or free LLM APIs for tiny fun project?

Hi, I'm looking for a free/opensource api to build a small GPT webapp for fun. I want to deploy it on something like Heroku and use Flask in the backend.


I'm also open to uploading a small-ish llm model on Heroku and use that to answer chat like queries from users.


Do you know of any such small foss models and/or free APIs?

api apis backend deeplearning flask free fun gpt heroku llm opensource project small