VTK's Qt Widget registration with Qt Designer/Creator ?

I have build VTK 9.1.0 from source on Ubuntu 18.0.4 with Qt 5.14.2

I understand there were some changes to naming of Qt related widget in VTK

Googling mentioned something called QVTKWidget which is a plugin Qt Creator/Designer will load so that the widgets show up in the UI for design purpose.

My build of VTK currently shows the following


Are the Qt Creator/Designer plugin shared library still being built or named differently ?

If they are no longer maintained/supported, I will design the Qt app in Designer via promotion method instead of drag and drop. I just wanted to confirm this before I use the alternative approach.

I have also come across this write-up which mentioned QDesignerCustomWidgetInterface but searching through the VTK-9.1.0 source does not show them up.