Hosting oAuth1 or oAuth2 Server

I understand there is support for external oAuthX providers, but if I would like to implement oAuth1 or oAuth2 with ServiceStack, is that supported? I would like to be able to build an API with ServiceStack where third party apps can use the logins of our API but with a grant from the user (as you see when you use Google, Facebook account for your app).
Is this possible?
I know there is a JWT provider but this only support sending uid/pwd through the client.

In .NET Core you’d typically use IdentityServer to create an OAuth Server, e.g:

I’d personally recommend keeping the OAuth Server independent from your Apps, i.e. treat it like a 3rd Party OAuth Provider and not try bundle it with your existing Apps.

Just to be sure I understand properly this template could be use for like an “Azure B2C” service and base on that provide an SSO solution for our different apps?

It’s for using https://identityserver.io as your Auth Server and includes integration examples of separate ServiceStack Web Apps and APIs that uses it for authentication.

See using IdentityServer4 Auth docs for more info about this template.