Okay, I managed to figure it out. Yes, this module is not available if using open source version of Qt but one can build it manually from source components and use.
This instruction helped me a lot: https://linzichun.com/posts/qt-mqtt-opcua-modbus-rest/#qt-opc-ua
Be ready to read the console, download some other missing stuff to your platform and repeat the same command, however. I needed to install about 4-5 missing utilities during the proccess.