You can't do that anyway. You can't put GPLv3 apps on the App Store. ProtonMail can put this app on the store, because they own it and can relicense the App S

You can't do that anyway. You can't put GPLv3 apps on the App Store. ProtonMail can put this app on the store, because they own it and can relicense the App Store build at-will. But no one else owns ProtonMail's code, so we can't take it, give it an App Store-compatible license, and publish it.