I couldn't figure out any way to change the user's email using FirebaseAuthentication.net v4. (I'm using .NET MAUI so I have to use the base library). While you can already do authClient.User.ChangeDisplayNameAsync(displayName) and authClient.User.ChangePasswordAsync(password), there is no method here that allows you to do this with a user's email for some reason.
If there is a way to do this already then I would like to know, but IMO, it should be moved to go along with the already available methods mentioned above. Otherwise, this is basically a feature request.