I am currently trying to implement OpenID Connect using Okta as my identity provider.
The only plugin I found that was capable of handling OpenID Connect was the Flutter AppAuth Plugin . Unfortunately I was not able to use it with a Native Webview in order to have a seamless experience for the end user or more especially to not have any navbar cf. image below:
Anyone was able to implement this flow as a native Webview ?
I don't believe you'll be able to do this in a native Webview. OAuth and OIDC are designed so the application never knows about the user's credentials - the application just receives an ID token and access token. If you tried to embed Okta (or any OAuth flow) in a native login, the application could get at the user's credentials, and possibly harvest them. Popping a browser is a more secure way of doing things.
To add to Matt's answer, AppAuth is the standard pattern here, which involves use of special InApp / system browsers:
My blog has some details on this. I always recommend people to start with AppAuth samples. A couple of posts:
