Authorization Code Flow using API (Without redirection)

All,

We are implementing Keycloak as IAM for Mobile App (built using react native.).

We would like to have our native experience of the login and MFA features instead of using Keycloak's UI and we would like to use Auth code flow for better security .

We are looking fordocumentation for following :

1. Auth code flow with PKCE but instead of using UI redirection, we would like to have it though OIDC APIs. No redirectino.

2. Customization of standard grant types or create new Grant types. E.g. Sharing one reference of how it works with WSO2 - https://is.docs.wso2.com/en/latest/references/extend/authentication/oauth2/write-a-custom-oauth-2.0-grant-type/

Please help.