Yep, we finally have our day one online functionality of the Nintendo Switch and can confirm that the main way to add friends will be using Friend Codes.

The options in the Add Friend menu are:

Search for Local Users

Search for Users YOu’ve Played With

Search with Friend Code (12 digit)

Sent Friend Requests

You can also add friends from Super Mario Run and Miitomo, which I’ve tested and it does work quite well.

Although, it looks like you’ll need to give someone a 12 digit friend code to add them if you haven’t played with them or aren’t in the same room.