But that is what I'm trying to say. There is no interoperability. Apple probably deleted that one chapter you referenced just to discourage people from doing it. You most definitely do not want to ever use "-fobjc-call-cxx-cdtors". If you do it correctly, then you shouldn't ever need it. If you do need, it, then you've done it wrong.
Here are a couple of remaining documents. They are fairly low-level and won't help you much:
https://developer.apple.com/library/content/technotes/tn2185/_index.html#//apple_ref/doc/uid/DTS10004200
https://developer.apple.com/library/content/documentation/DeveloperTools/Conceptual/CppRuntimeEnv/CPPRuntimeEnv.html#//apple_ref/doc/uid/TP40001666
Can you describe how you were intending to wrap this library? They key is that Objective-C is just C and nothing else. There are some low-level, highly-optimized C functions that do the messaging magic and make it into an OO language. The brackets are just syntactic sugar. But because it is C, you can make use of the fact that pointer types don't matter. You can create pointers to C++ object and they can exist in C and Objective-C. Your Objective-C++ source code can recognize that those pointers are to C++ objects and use them. They must be C++ pointers though. That is the only way to bridge the languages.
And if you think about it, pretty much every structure in any high-level language is going to be a pointer. So that is why I can say there is no interoperability while describing how to do it. If you are clever enough with the pointers, you can have Swift work with literally any language. You will always have to have a C layer to bridge the pointers. Objective-C++ just happens to include that C layer natively.
What is your target platform anyway? If you are on a Mac, you can also wrap your C++ code in a stand-alone executable or XPC and call it that way. Depending on what you are doing, this may be just as fast and/or something you need to do anyway. Don't forget, your C++ library might assume you have C++ exceptions too. You can't let those escape into Swift.