How to get a generic callback function or method with any types of return or parameters?

I'm making some API and want to allow app developers to put their own callback function with any return types and any number of parameters. Below code is example I expect to work. I wonder how to define ?<?> userfunc in MyAPI.h

// MyAPI.h

using namespace API {
/**
* Executes callback function after a random time in its own thread.
* @param userfunc User defined callback function.
**/
void SetCallback(?<?> userfunc);
}

// application.cpp

#include "MyAPI.h"
#include <chrono>
#include <format>
#include <iostream>

std::string get_current_datetime() {
  const auto now = std::chrono::system_clock::now();
  return std::format("{:%d-%m-%Y %H:%M:%OS}", now);
}

bool callback_1(bool* triggered, std::string* registration_time) {
  *triggered = true;
  std::cout << "CALLBACK_1" << std::endl;
  std::cout << "registered: " << registration_time << std::endl;
  std::Cout << "triggered : " << get_current_datetime() << std::endl;
  return true;
}

int callback_2(int* triggered) {
  *triggered = 1;
  std::cout << "CALLBACK_2" << std::endl;
  return 1;
}

int main(void) {
  bool is_triggered_bool = false;
  int is_triggered_int = 0;
  std::string curr = get_current_datetime();
  API::SetCallback(std::bind(&callback_1, &is_triggered_bool, &curr));
  API::SetCallback(std::bind(&callback_2, &is_triggered_int))
  Sleep(3000);
  if (is_triggered_bool && is_triggered_int == 1) return 0;
  else return -1;
}

Any advice will appreciate