qtnetwork doesn't load the default system ca bundle on ubuntu

We have a self-signed ca certificate installed in Windows, macOS and Ubuntu, on Ubuntu the self-signed ca cert is install in /etc/ssl/certs/ca-certificates.crt.

These code snippet below works fine on both Windows and macOS, but doesn't work on Ubuntu 22.04.3 with kernel 6.5.0-26-generic. In order to work for Ubuntu, it have to load the ca bundle using  QSslCertificate::fromPath, and set a new QSslConfiguration for QNetworkRequest.

m_url = "https://self-signed-https-domain/path"
QNetworkRequest request(m_url);
// uncomments these 4 lines below on Ubuntu
//QList<QSslCertificate> certs = QSslCertificate::fromPath("/etc/ssl/certs/ca-certificates.crt");
//QSslConfiguration config = QSslConfiguration();
//config.addCaCertificates(certs);
//request.setSslConfiguration(config);
m_reply = manager->post(request, params.toUtf8());

The QSslConfiguration::defaultConfiguration() method doesn't load the default system ca bundle too.