This weekend, August 27th and 28th 2022, is Splatoon 3's first Splatfest. It's free on Nintendo Switch to download. this video shows me going through the character creation, tutorial, and exploring the city of splatsville. There's no online multiplayer in this video as it was not on when i logged in. i assumed that it started today, 27th, but it appears that online multiplayer starts on the 28th in japan.