This is not Julia-specific, but I’d like to post this anyway since I think Julia could be really good for it. Julia is a fast and easy language, which could be quite suitable for a reinforcement learning environment.
Pufferlib is written in Python, which Julia interoperates with really well. Moreover, the library was written in a way that allows interaction with any environment, be it C, Rust, Go, etc, and obviously Julia. To be effective, it only requires that the environment be fast enough.
If you want to introduce the machine learning world to Julia, here is your chance. Write a reinforcement learning environment in Julia and connect it to PufferLib.