@CiblesGD there is no such thing as Nintendo Network on the Switch, so you’re pretty much just linking your Nintendo Account... the Wii U doesn’t support Nintendo Accounts, only Nintendo Network IDs and the accounts that you make with the system.

so yeah, it is not possible to link it... but I think you CAN link the Nintendo Network ID you used to make your Nintendo Account

but i didn't use a nintendo network id to make my nintendo account ;~;

actually, there is no such thing as a Nintendo Network ID on the Switch as it has been replaced by Switch Online... Nintendo even said that Nintendo Network IDs cannot work on the Switch

so what are you actually trying to link if NN IDs don’t work