Ok, I figured it out. Unfortunately, the Qt installer is not so intuitive (at least not for me). Selecting "WebView" as a component in the installer does not mean that the corresponding libraries are automatically added. By default, Qt only installs the mingw program chain, and this tool chain cannot compile WebView / WebEngine. To use WebView / WebEngine, you must select the pre-compiled Visual Studio libraries in the installer. In addition, Visual Studio must be installed on the system. After installation, make sure that Qt Creator uses the Visual Studio compiler (you can specify this in the Qt Creator build set settings).
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