Can I put a dummy app in the App Store to install a GPL app?
This is not possible. Apps can't download other apps.


  2.5.2 Apps should be self-contained in their bundles, and may not read or write data outside the designated container area, nor may they download, install, or execute code, including other iOS, watchOS, macOS, or tvOS apps.


https://developer.apple.com/app-store/review/guidelines/#software-requirements