An (third-party) app can use a nextAuth-enabled app for performing authentication. In this case the nextAuth-enabled app will handle all authentication aspects, and will, after approval/rejection by the user, return to the caller app.
By using the getQrLogin or getQrEnrol API calls, you can obtain a byte array containing the data that is displayed in the respective QR codes. Using unpadded URL-safe base64 encoding to represent the binary data, you can build a Deep Link URL that will open your nextAuth-enabled app and trigger the relevant action.
https://<deep link domain>/<prefix>/<data>
You can specify the chosen path prefix in the app's configuration.