Please view the MoPub Unity SDK changelog, MoPub Android SDK changelog, and MoPub iOS SDK changelog for a complete list of additions, fixes, and enhancements across releases and platforms.
Starting in MoPub Unity Plugin 5.6, the MoPub iOS SDK is no longer included as a bundled framework and is instead specified as a dependency via podspecs. Upgrading from previous versions will leave the previously bundled iOS SDK framework, which needs to be removed to avoid collisions with the podspec dependency.
To address this, please delete the following directory from your project prior to building for iOS with the MoPub Unity Plugin 5.6: Assets/MoPub/Plugins/iOS/MoPubSDKFramework.framework