Splunk has released a new version of this app, called the 'Upgrade Readiness App'. For various reasons, it was required to create a new app rather than update this existing app. The new app is available at this link: https://splunkbase.splunk.com/app/5483/
This app in its current form will not receive any new updates, and will eventually reach End-of-Support once a Cloud-compatible version of the 'Upgrade Readiness App' is made available. Admins of customer-managed environments are recommended to upgrade to this new app, which has received many updates.