Projects for Apple platforms usually also use .h, where it could mean anything from C/C++ to Objective-C/C++.
In practice, Clang handles mixed C/C++/Obj-C codebases pretty well and determining the language for a header never really felt like an issue since the API would usually already imply it (declaring a C++ class and/or Obj-C class would require the corresponding language to consume it).
If a C++ header is intended to be consumed from C, adding the usual should alleviate the name mangling issues.
That’s mostly still true, with the small caveat that the default prefix on arm64 macOS is /opt/homebrew rather than /usr/local, so you might have to add it explicitly to your PATH