> And they should still be banned from forcing apps to do it under their arbitrary judgements in order to participate on their platform. That isn't the same thing as preventing them from doing it.

If they do it and it's enabled by default then they still get to grief their competitors because by default anyone who tries to use the competitor gets a big scary red box that deters adoption and has to jump through a bunch of hoops to get past it. It also thwarts adoption of competing signing alternatives because >90% of people will use whatever the default is even if the alternatives are at least as good.

> some people honestly need walled gardens

"Walled garden" is an Orwellian term. It's meant to imply that someone is curating what's inside it and not letting in things you don't want, and that is indeed a useful thing. But then people use the same term to mean a "garden" that locks you inside of it rather than locking bad things out. The only people who need that are small children and adults with mental illnesses severe enough to justify them having a guardian assigned to make their decisions for them.

> I'm also not sure that attestation should be banned at the app store or platform level; it's a service.

It isn't a service at all. The device contains hardware to sign the state of the device using a protected private key. Solving the problem is very simple -- you ban the device from coming with any private key already installed that the user can't freely extract. Then the root of the chain of trust is the customer's public key, not the vendor's, and whether a device is authorized comes down to whether the user's public key is authorized rather than the vendor's, which in turn makes the system vendor-agnostic.

> That's just DNS. If your platforms service becomes hostile, there will be cheap/free competitors, just like DNS.

DNS is actually a pretty terrible model because the "competition" is a fraud. There are registrars and registries and the registrars compete with each other but the registry still sets the price the registrars pay and the registries have a monopoly over every name in that TLD, so the competition can't actually get you a lower price than the monopoly registry itself sets. And the registries only compete with each other to the extent that you think that example.dental is valid substitute for example.football (no, sorry, those are both the same registry anyway) and to the extent that example.co.uk is a domain you could get instead of example.com rather than needing both. Meanwhile ICANN charges an extortionate amount to anyone who wants to become a registry and the entire system is set up to encourage squatting, to the point that the registries are now doing it themselves rather than making any attempt to impede it.

In general if you want something to work well you need to make it a protocol rather than a service. As soon as you allow a central chokepoint to exist you'll have a troll jumping out from under the bridge and trying to collect tolls.