How to Invite Friends and Voice Chat Using the Nintendo Switch Online App
As of 29 July 2021, the Online Lounge feature of the Nintendo Switch Online app was discontinued. As a result, it is no longer possible to arrange or join Splatoon 2 online battles using a smart device.
You can continue to start a local or online multiplayer game in Splatoon 2 without using the Online Lounge feature and can also continue to use the other Splatoon 2 services in the Nintendo Switch Online app, including voice chat with friends.
For more information, see Splatoon 2 Online Lounge Discontinuation.