I assumed that https://hub.docker.com/r/discourse/discourse was already used by the normal installer and that https://github.com/featheredtoast/discourse-docker-compose was just featheredtoast having a go to get composer to work, but with the link you gave me I can see that is it more than that, this is a genuine effort to make this a thing.
I will keep an eye out on that thread.
Really helpful, thanks.