The logical next step would be to require devices sold in the country to only be able to use legal app stores, where "legal" is defined as "complying with the requirement to block any E2E apps without backdoors".

Everything is already in place for this, both hardware- and software-wise.

What, and mandate you have some authorization to maintain your ability to access software or to use electronics of any sort that doesn't have a compliant application store?

Nope, just ban importation of such devices. Existing ones will join the waste heap soon enough, and then why bother banning the activity if any device capable of it is inherently contraband?

> There are other methods of distribution than app stores.

And all of them are completely irrelevant because only us nerds would even know about them let alone how to use them.

> People didn't buy their copy of Napster from GameStop back in the day

Those days are long dead.

There isn't some magic bar of comprehension or indecipherable encoding. People will gravitate to acquire what they desire, regardless of prereqisites.