RemObjects Iodine is a great native fit on each individual platform, giving you full access to all the native APIs, frameworks, UI widgets, and so on:

• .NET - The .NET platform includes the regular .NET Framework, as well as Mono, .NET Core, ASP.NET, WinRT and Universal Windows Projects. .NET is a great target for writing Windows GUI apps, cross-platform servers (to deploy with .NET Core or Mono), command line tools, and websites.
• Cocoa - Build apps for Apple's macOS, iOS, iPadOS, tvOS and watchOS, based on the Cocoa frameworks. Code interacts directly with Objective-C runtime classes and APIs, and also has full access to lower-level C and POSIX APIs.
• Android - Build applications for Android, both using the regular Java-based Android SDK as well as extensions using the native Android NDK (using the same language!). SDK applications give you full access to the standard Android APIs, while Android NDK extensions are great for high-performance or low-level code in Android apps that cannot easily be achieved on the Java level.
• Java - Build projects for the Java Runtime and related platforms. Your code will be compiled to Java byte code that can run anywhere the Java VM is supported.
• WebAssembly - Build modules that can run in the browser and interact with JavaScript and the HTML Document Object Model.
• Windows (native) - Build CPU-native Windows projects against the lower-level Win32 API or using Delphi RTL/VCL.
• Linux - Build CPU-native Linux projects against the low-level libc and POSIX APIs.