hi @pkt may I know what docs did you tried followed?. Wdym by Auth Method set to None?. Maybe you can read about various auth methods Zitadel has to offer to clear up your understanding on it https://zitadel.com/docs/apis/openidoauth/authn-methods
I might have to test and see the behavior for token introspection for Native applications, meanwhile can you pls try to change the Auth type and see if you can generate the token with it (the links I pasted above helps you with it)