Oooooh, I actually didn’t think about this. Thank you for the idea - the main reason why I was looking for an OAuth approach is I can retrieve the user by the external ID. I’m going to see if I could potentially retrieve a user by a user field.
EDIT: Ok, I actually might have a way of doing this using the custom fields. I’m probably going to just have to use an external database and make my own way of requesting a Discourse user from their Minecraft UUID. I just don’t know enough about the limitations of Discourse to know if there’d be a better way.
EDIT 2: Hmm, I don’t see a way to edit custom user fields via the API. I ideally wanted to have it only get set by the API, so it is guaranteed that they own the account. I might just need to make an external database and do account linking through something else.