New versions of the Flat File Importer module have been published on github:
Version 5.5.0 is currently awaiting approval for the appstore and after that release has been approved I'll try and add the other versions to the appstore. Hope this will help you in importing your data in newer versions of Mendix.
Well the AppStore says Erwin 't Hoen?
Community Supported content is taken care by the community itself. So the creator of the content is responsible for maintaining Community created content. https://docs.mendix.com/community/app-store/app-store-content-support