XCode: 12.4 or lower | Appodeal SDK: 2.10.1+
The error Undefined symbols for architecture arm64: "_OBJC_CLASS_$_SKAdImpression" during the iOS build usually happens if XCode or CocoaPods version is lower than required.
The error log example:
To fix it update XCode to 12.5 or higher and CocoaPods to 1.10.0 or higher.
To update CocoaPods to the latest version, open Terminal and perform the following command: