That's .NET Native, which is a completely different beast unfortunately. .NET Core is set to add support for ARM64 in .NET 5. Furthermore many .NET apps for Windows were built using WPF, which won't support ARM64 until .NET 5.
So plenty of stuff is available.
Besides it is not like one can blindly run .NET on other platforms, because plenty of applications make use of COM or DLLs written in C++.