Without native bindings, you'd still need to write all the UI code in C, and then you could use Swift interop to call your C function that does the layout. That's not what most would think of as Swift support if you're writing C.

Swift call C++ code with Bridge

Java call C++ code with JNI

You can get more details here:

https://github.com/idea4good/GuiLitesamples

Yes, but not C++ code. Also, many environments, such as Linux, don't support the Objective-C runtime at all.