The Qt Quick documentation should be checked for things that need to be changed, updated or removed due to the QRhi-based rendering path. The mentioning of "OpenGL" and QOpenGL* class references are the main things to look for.
In 5.14/5.15 the scenegraph-related pages have been updated and rephrased as much as possible to apply to both rendering paths, and this has been updated in dev further. Furthermore the QSG classes (and some related QQuick*) received lots of doc updates during the RHI porting. The situation is pretty good.
With some grepping it seems that what's left to do in this task are:
- QQuickWindow: especially the class documentation needs revising. It seems it is currently from the 5.0 times, not mentioning even the Qt 5.8 changes (like the software backend).
- ShaderEffect. All concepts apply as-is, but example snippets, and OpenGLisms need changes.