What's the issue of Apple Runtime choosing what's running? You are buying a bundle of apple hardware+runtime, that's what's in the box. For hardware that you can replace the OS choose another device.

To me the solution seems more with being able to choose which OS I can put on some metal. iOS is very sepecific OS for a specific metal, it shouldn't need to cater to everything.

The thing about Android and windows in the past (about IE and GApps) is very different in Apple's as it is selling a combo. That metal-runtime integration, those envirnment consistency, that cathedral instead of bazaar, is why people buy iphones, not Androids or Libres.