https://www.gamespot.com/articles/nintendo-switch-online-service-offers-20-free-nes-/1100-6458799/

After months of silence, Nintendo finally shed more light on its premium online service for Switch. The subscription service launches this September and is required to play games such as Splatoon 2 and Mario Kart 8 Deluxe online, but it also comes with some additional perks for subscribers, including a library of classic titles.

Nintendo will offer subscribers to the Switch online service access to a selection of NES games as part of its "NES - Nintendo Switch Online" program. At launch, the lineup will consist of 20 titles, although the company says that more games will be added to the library "regularly."