> To have government apps work only on iOS and Android is perfectly reasonable in the current state of the world where this covers 99% of smartphones.

the fundamental flaw with that approach is that it is totally unreasonable to have government apps in anything other than open source and fully public systems. nothing else can really be trusted, and any private/closed source option should be disqualified from the get go.

the reason is simple: you can't trust private entities or opaque systems, and you can't trust government either, thus the solution has to be fully transparent or you're doing nothing.

the problem with that is that it is hard, expensive and/or inconvenient.

Why should I have to have a smartphone to have a digital wallet? Smart watches, tablets, laptops, portable game consoles, etc, are all perfectly cromulent hardware for running a digital wallet.