A Lua backend would be pretty neat. Making a backend is definitely a challenge but there is at least one example of a community-made backend, this one is for Python: [Idea] Python backend. See that discussion for links to the Slack channels and repos.
I’m not sure if it uses the new IR or not. It’s passed a lot of the backend unit tests and has been under active development until this last June when they paused development until they get more resources (see the Slack channels).
Good luck!