Eu diria no mínimo 3

I don't think everyone on Nostr today is a power user and many people do have more than one client app installed. On iOS almost everybody has Primal and Damus. On Android, almost everybody has Amethyst and Primal. That is on top of the 0xChat, KeyChat, Fountain, Nostur, Coracle, Jumble, Habla.news, Yakihonne. These apps don't do the same thing people will have more than 10 apps in every phone for sure.

More than 1 client per device? I doubt it... I run #amethyst on mobile and #coracle on desktop

There's a large amount of people that only use primal. I think after it got attention from people using it's inbuilt wallet to buy goyslop at shakes and steaks when they started accepting Bitcoin