I’m still working on iCloud capabilities but I’m stuck adding the entitlements in Defold properly. I’ve posted the problem details in this question to the forum: How to properly add iOS entitlements to an app?
The good news is, I’ve since found out that the Unity Game Center plugins that have the GKSavedGame feature require iCloud capabilities to work. So, when I can get iCloud entitlements added properly it’s looking like Save Game is possible.