I have an AVM FritzBox router with UPnP enabled, easily Germany's most-used and most-loved router model. Everything that uses UPnP works out of the box, but I've never seen the Switch create UPnP rules on its own.

I wonder what the fuck keeps Nintendo from operating their own STUN/TURN servers, at least for their own fucking games where I pay 35€ a year for their online service.