I would say that this approach is 100% allowed by Apple, as it doesn't allow device tracking between different apps (specially if you skip the IFA step). That w

I would say that this approach is 100% allowed by Apple, as it doesn't allow device tracking between different apps (specially if you skip the IFA step). That was the main concern of Apple, that lead to disallow developers from accessing UUDID, mainly because it allowed advertising services to cross usage data between different apps. Using Keychain to store your UID just ensures you don't lose your UID, not a system-wide UID.