Workaround

#include <QCoreApplication>
#include <QTimer>
#include <QtGlobal>
#include <QSerialPort>
#include <QSerialPortInfo>
#include <QDateTime>

#include <thread>


typedef enum {
    SUCCESS,
    ERROR
} ErrorCode;

// Initialize QCoreApplication and quit after 11 seconds
void initQCoreApplication(int argc, char* argv[])
{
    QCoreApplication app(argc, argv);
    QTimer::singleShot(11000, &QCoreApplication::quit);
    app.exec();
}

// Read serial port for 10 seconds and print data
void readPort(QSerialPort* port)
{
    for(qint64 startTime = QDateTime::currentSecsSinceEpoch()+10;QDateTime::currentSecsSinceEpoch() < startTime;)
    {
        if(port->waitForReadyRead(100))
        {
            qInfo("Read data %s", port->readAll().constData());
        }
    }
}

int main(int argc, char* argv[])
{
    std::thread appThread(initQCoreApplication, argc, argv);

    QSerialPort port("COM10");
    if(!port.open(QIODevice::ReadOnly))
    {
        return ERROR;
    }

    // Make sure that QCoreApplication has been instantiated
    while(QCoreApplication::startingUp())
    {
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
    }
    // Moving the object to the applications thread is crucial
    port.moveToThread(QCoreApplication::instance()->thread());

    std::thread thread(readPort, &port);
    thread.join();

    appThread.join();
    port.close();

    return SUCCESS;
}