what theoretically yes, but there are multiple of Flarum's features that depend on email and expect every user to have a valid email address, so you would have to disable those features as well.
I think there are extensions to disable email verification and to disable some of the email notifications, but a new extension might be needed to remove all email UI.
Also Flarum's password recovery feature only works via email, so without a valid email users won't be able to reset their password.
