Angular FE and Asp.Net Core Backend API

We are using Angular front end app and dot net core backend APIs. user authentication from angular app is working fine. but what would be the various options If we want to expose the APIs to another service and wanted to do service to service authentication. we don’t have client secret as we registered angular app as single page.

Are you referring to client credentials flow when you mentioned service to service authentication? If yes, you might want to create a separate app for it (Web).