Qt5 comes with QtWebView (see here http://doc.qt.io/qt-5/qtwebview-index.html).
I guess it's due to the older version of QtWebEngine (qt5-webengine-5.9.5) that has been left along with Qt-5.12, qt5-webview isn't available.
The projects that require webview aren't portable until qt5-webview becomes available.
Ah, we seem to be missing a port for that, let me fix it, hopefully it is happy with 5.9.5, otherwise it will have to wait for 
A commit references this bug:
Date: Sun Jan 13 10:14:24 UTC 2019
New revision: 490122
New port: www/qt5-webview
Qt WebView provides a way to display web content in a QML application without
necessarily including a full web browser stack by using native APIs where it
Please let me know if its not working :)
(In reply to Tobias C. Berner from comment #3)