When do you need to use Okta OIDC library or SDK?

I have a C++/QT app through which I have to let users sign on/in to our organization’s Okta SSO. After reading through documents, I understand these are my 2 options:

  1. Create custom UI within the app to facilitate login like in the following example
    https://developer.okta.com/docs/guides/build-custom-ui-mobile/android/before-you-begin/

  2. Open a browser to let users sign in like in the following ex
    https://developer.okta.com/docs/guides/sign-into-mobile-app/android/before-you-begin/

But these examples use OIDC library and Authentication SDK. I did not find this library and SDK for a C++ app. Are these really needed or just to make implementation easier?
I am very new to Okta. so any help is appreciated.

Okta doesn’t have anything for C++ really as it’s all web related stuff. But you can use plain HTTP requests/response to build your own flow.

Just check Okta Authentication API, it can help you with authentication of your users.