Is your grandma REALLY tied to some ecosystem?

Is she a Visual Studio Code developer? Does she need to manage Docker containers?

Security does require new hardware because iOS is leaps-and-bounds better than any other system.

There is no other option. Nothing else comes close.

I mean, if you agree that the only option for mass adoption of password managers is to get people to shell out $$$+ for new hardware and switch ecosystems, I rest my case.

Not sure what your case is?

Were you expecting security in broken systems like Android? Instead of forcing security onto a broken system, just avoid that system?

The fist step of security: stop using Android.

And you haven't explained why your grandma is tied to an ecosystem. I'm honestly asking if she's a developer or not?

What is her use case? Why does she need to be on a specific platform?

As developers we might be used to paying 100s of euros (or signing up to a contract to effectively do the same over time) on a phone, but the point is $grandma may not be willing to spend even 20% of iPhone budget (and definitely not replacing it by the time OS updates end)

You don't need to be a developer to be tied to an ecosystem. Maybe she wouldn't want to lose her Candy Crush purchases?