Minimum iOS version for the Storyteller app -- is there an iOS 15 build?

I have an older iPod that cannot be updated past iOS 15, but the Storyteller app requires iOS 16. Is an iOS 15 compatible version possible?

Resolution: No, and it is not planned. The v2 app requires iOS 16 because Storyteller implements media overlay playback itself using Swift features introduced in 16; that requirement can only be revisited once the Readium toolkit ships media overlay support and Storyteller switches to it. The v3 apps raised the floor further, to iOS 18 (Android's floor is 9), because on-device alignment with storyalign was added; dropping v3 back to iOS 17 would be straightforward and 16 doable with some work, but 15 is effectively a UI rewrite -- NavigationStack, NavigationPath, presentationDetents and LabeledContent were all introduced in iOS 16, and the alignment dependency cannot be conditionally compiled out without vendoring it. On an iOS 15 device, use the web reader in a browser instead of the native app.