Update bbc sounds on ipod 6th generation

If you try the update option in the App store, you will see a message telling you that the current version requires iOS 15, but your iPod will be using iOS 12.5.7, which means that the latest version cannot be installed on your iPod. The message goes on to ask if you would like to download a compatible version:

When I tapped the Download button, the screen simply re-displayed the same message, suggesting that the version on my iPod is the "compatible version". That would appear to be 2.16.0.18293, which I found in My Sounds/Settings in the app.