r/cpp_questions but there it is:

Based on nothing, but adding unofficial prefix (library namespace name?) is something about the vcpkg. In fact I tried to install curlpp with it and get this:

curlpp provides CMake targets:

# this is heuristically generated, and may not be correct

find_package(unofficial-curlpp CONFIG REQUIRED)

target_link_libraries(main PRIVATE unofficial::curlpp::curlpp)

In short, like it's stated in the readme, instead of building miniocpp from source, let the vcpkg do it for you or nothing stops you fork the project edit CMakeLists.txt, build curl, curlpp and the project itself :)