Objective-C++ main point of existence, just like POSIX, was only to bring other software into the platform.
It is quite telling that only old timers have access to Objective-C++ docs.
The obj-c drivers from next/OpenStep were replaced with a restricted subset of C++ (not objective-C++) IOKit system. I'm not sure what system GP is referring to based off Obj-C++ but I assume it's not the drivers?
Ironically I think IO Kit userspace replacement, DriverKit, got its name as homage to the Objective-C one in NeXTSTEP.
Objective-C++ main point of existence, just like POSIX, was only to bring other software into the platform.
It is quite telling that only old timers have access to Objective-C++ docs.