So I have to setup authentication in my flutter app which needs to follow the good practices, I am using .net with abp.io on the backend which configures most of the openID for you, just need suggestions on what and how to implement the authentication, I have come across articles which suggest to use the PKCE code exchange due to it not having any client_id or secret. Alos I am confused in it’s implementation in flutter, if there is a resource for it, do share.
also is there a way to implement this and follow best practices and also keep the use in-app all the time, so the user isn’t redirected to a web-browser or in-app-webview?

I have implemented the auth-code flow in external browser as well as in-App-Webview, and all of that is working pretty smoothly.