I’m making more progress. I believe I wasn’t using my distribution cert for signing, because when I turn it on for sure packaging fails with something about get-task-allow entitlements, so it never would have returned available in-app purchases anyway.
But back to the Online Subsystem problem. I’ve also tried figuring out which Online Subsystem plugins need to be turned off. I’ve turned off everything except Online Subsystem, Online Subsystem Utils and Online Subsystem IOS, but I get this message during packaging:
UATHelper: Packaging (iOS): LogModuleManager: Warning: No filename provided for module OnlineSubsystemIOS
UATHelper: Packaging (iOS): LogModuleManager: Warning: ModuleManager: Unable to load module 'OnlineSubsystemIOS' because the file '/Users/Shared/Epic Games/UE_4.18/Engine/Binaries/Mac/' was not found.
UATHelper: Packaging (iOS): LogModuleManager: Warning: No filename provided for module OnlineSubsystemNull
UATHelper: Packaging (iOS): LogModuleManager: Warning: ModuleManager: Unable to load module 'OnlineSubsystemNull' because the file '/Users/Shared/Epic Games/UE_4.18/Engine/Binaries/Mac/' was not found.
I’ve disabled OnlineSubsystemNull after it was suggested by several answerhub posts, but otherwise I can’t find a solution to this error.