How to achieve Custom User flow for Mobile apps using Native screens

I am developing a native app for Android and iOS using Flutter. I want to use Key Cloak for the authentication. I have my own user flow for Signup using Phone number followed by Email verification and these are native screens. From Key cloak examples and docs it seems like for Key cloak authentication, sign in user flows will be a web page loaded from system’s browser.
Is there a way I can use native UI screens as the sign up flows?
This is because I do not want my users to switch to browser for the Authentication process rather I would prefer my users to be in my Native app. Kindly help.