You could download the app, disconnect Wifi and Ethernet, run the app and the reclamation process, remove the app (remember, you have the guarantees of the macO

You could download the app, disconnect Wifi and Ethernet, run the app and the reclamation process, remove the app (remember, you have the guarantees of the macOS App Store so no kernel extensions etc), and then reconnect. Edit: this might not work with the payment option actually. I don't think you can IAP without the internet.