Flutter is not the official Android SDK. Mono is not meaningfully cross platform and is not the official Windows SDK. The iOS SDK is not cross platform and ch

Flutter is not the official Android SDK. Mono is not meaningfully cross platform and is not the official Windows SDK. The iOS SDK is not cross platform and changes frequently leaving behind it a trail of dead x-platform projects like the one you cite. I suppose there are multiple reasons for this lack and it may not be a deliberate strategy in all cases but there is no incentive to promote cross platform work and there are multiple incentives for corps not to. These platforms are made to corral users and devs, not to share them.