You could take a look at setting a single Allowed Callback URL for all applications, once the user is authenticated, they will be redirected back to the Callback URL so this could be your login app.
I recommend taking a look at our Quick Starts to see how / where to configure the Callback URL for your specific application.
On the error details, you should be advised about a Callback URL mismatch with a URL that is not in the list of allowed callback URLs.
In this case, you will have to make sure that your application is calling one of the Allowed Callback URLs for your app. If this is correct, then please make sure your login request’s redirect_uri points to your callback URL.