That's not how monopolies work, though.
When Ford sells me an F150 I don’t cry about them having a monopoly on their Sync platform. That’s not now monopolies work
And what about the other mobile platform (singular)? That one’s also making it harder and harder to sideload apps.
Apple has neither a monopoly on phones nor on app marketplaces.
Maybe monopoly is not the right legal category, and maybe what they are doing is perfectly legal and always will be, but I don't think the fundamental point can be argued away with analogies like these.
Still not any kind of monopoly