Totally works! It seems like the fact this works should make it easy for Apple to find and fix the bug, but apparently not.

Sorry, late to the game. In 2025, is this the way? MKCircle says it's not meant to be subclassed, but doesn't specifically say it will break things. I got a subclass of MKCircle working fine when calling a "convenience" initializer of MKCircle. Ditto MKPolyline. But not MKMultiPolyLine. It crashes with unrecognized selector sent to [ points], once subclassed, even when initialized with its primary initializers, and a var member set externally.

Same here. Thanks - could you expand on your solution, I don't follow? I've tried putting the @available at the root of var body, I tried using a ViewModifier, but still I get the same crash on 14.x.