It was technically possible for a service to do OAuth2 with NNIDs if you somehow obtained Nintendo’s permission to do it.
I know that OAuth2 is possible with Pretendo as you sign in to this Discourse forum with it, but is it possible for me to use it if I created a web app and wanted to let people sign in through their PNID?
This isn’t currently possible, and I’m not aware of any plans to implement this. I personally think it would be cool to have (maybe fitting in with the 3rd party server support plans), but I don’t know whether it would be a priority for the team overall.
Maybe @PN_Jon would like to comment on this?
It’s one of those “I mean I guess why not” things for the future. I won’t say there’s no plans, but it’s definitely not a huge push