@forca maybe you need to do some additional steps
From QSslSocket documentation:
Describes the peer verification modes for QSslSocket. The default mode is AutoVerifyPeer, which selects an appropriate mode depending on the socket's QSocket::SslMode.
QSslSocket will request a certificate from the peer, but does not require this certificate to be valid. This is useful when you want to display peer certificate details to the user without affecting the actual SSL handshake. This mode is the default for servers. Note: In Schannel this value acts the same as VerifyNone.
And looking at this QWebEnginePage browser example, check the Downloading Favicons code snippet, which may help you accessing the underlying QSslSocket