Expose C# service to C++ COM client

  c++, com, dll, service

I have lot of function calls and back events in an .NET dll.
which I want to expose above as service.
This new service will be consumed by new .Net application and an old COM C++ application.(two way communication since events with data will be fired from service to clients and client will make function call on service)
I know we can use WCF or GRPC to do this.
But WCF is dead and GRPC depends on IDL/Proto file which i want to avoid.
Are there any other possible solutions which are simple.

Source: Windows Questions C++