How to Modify Duende IdentityServer 6.2.3 in .NET Core for Google Authentication with Refresh Tokens?

Question

Background

I'm working on a a .NET Core project using Duende IdentityServer version 6.2.3. We have successfully been using Azure OIDC as identity providers for a while. I now need to implement a flow where my application can receive refresh tokens from Google.

It seems that the Google's OAuth/OIDC implementation uses the access_type=offline parameter in the authorization request to obtain refresh tokens, as opposed to the standard offline_access scope used in other OpenID Connect (OIDC) implementations. (Sources: Refresh tokens - Google OIDC docs, The OpenID Connect Authentication Handler - Duende IdentityServer docs)

Questions

1. If I understand correctly, it seems Duende Identityserver does not support adding the access_type=offline parameter to authorization requests out-of-the-box. Is that correct? If no, how do I configure it?
2. If yes on 1: how do I extend IdentityServer to Include the access_type=offline parameter in these requests to ensure that my application receives a refresh token from Google?

Any examples or pointers on where to start would be greatly appreciated.

Thanks in advance!