If somebody googles for Qt Quick 2D Renderer, he hits multiple places and blog posts. If he finally hits the landing page at https://doc.qt.io/QtQuick2DRenderer/index.html , he is confronted with a lot of detailed information on how to build from source etc, but misses information a) where to get it and b) with which Qt versions it is compatible with.

IMO the landign page should state
a) that it is a commercial add-on, available only in Qt for Device Creation
b) that it is only compatible with Qt 5.4 - Qt 5.7.
c) That from Qt 5.8 onwards, functionality is merged into Qt Quick.