I was playing with the Ubuntu SDK today and noticed that there was no QWebView widget available for my forms, even though I have every Qt WebKit package under the sun installed.
It looks like the SDK’s version of the Qt designer is not looking in all the usual places for the related library. At least, not in the current version in the repos, as installed on Ubuntu 17.04 alpha. Here’s the fix:
sudo ln -s /usr/lib/x86_64-linux-gnu/qt5/plugins/designer/libqwebview.so /usr/ubuntu-sdk-ide/lib/Qt/plugins/designer/libqwebview.so