iOS app conversion tracking cannot be set up using:
- Server-to-server (S2S)
- Codeless conversion tracking
- Install confirmation feedback
iOS app conversion tracking is available for AdMob and YouTube, but not supported on mobile search or mobile display. Unlike conversion tracking for Android, where Google offers a codeless alternative, iOS requires either installing a tracking code through the SDK or setting up a server-to-server conversion feed. You can track 2 types of conversions for iOS mobile apps: app downloads and in-app conversions.
Read more here: https://support.google.com/partners/answer/6209179?hl=en