The Qt WebEngine binaries on Windows depend on Qt6WebChannel, Qt6Positioning, but this is not enforced in the installer. So you can install WebEngine for Qt 6.8.1, but all the examples will fail to build.

How to reproduce

Install Qt 6.8.1 through the online installer. Do not select any additional Qt 6.8.1 packages except Extensions > Qt WebEngine > Qt 6.8.1 > MSVC 2022 x64.

Open a Qt WebEngine example - like 'WebEngine Quick Nano Browser' in Qt Creator. This will fail at the cmake stage with:

[cmake]   Found package configuration file:
[cmake] 
[cmake]     C:/Qt/6.8.1/msvc2022_64/lib/cmake/Qt6WebEngineCore/Qt6WebEngineCoreConfig.cmake
[cmake] 
[cmake]   but it set Qt6WebEngineCore_FOUND to FALSE so package "Qt6WebEngineCore" is
[cmake]   considered to be NOT FOUND.  Reason given by package:
[cmake] 
[cmake]   Qt6WebEngineCore could not be found because dependency Qt6WebChannel could
[cmake]   not be found.

Install the missing package 'WebChannel' in the installer, re-run cmake. This will then fail with:

[cmake]   Qt6WebEngineCore could not be found because dependency Qt6Positioning could
[cmake]   not be found.

Also installing the 'Positioning' Add-On manually will make sure that the example loads & compiles.