I'm pleased to announce AdaStudio-2021 new release with VTK-9.1.0 support, many new examples.
It based on Qt-6.2.1-everywhere opensource expanded with modules from Qt-5.15: qtgraphicaleffects qtgamepad qtspeech qtx11extras qtwinextras
Qt6ada version 6.2.1 open source and qt6base.dll ,qt6ext.dll (win64),libqt6base.so,libqt6txt.so(x86-64) built with Microsoft Visual Studio 2019 x64 Windows, gcc x86-64 in Linux.
Package tested with gnat gpl 2020 ada compiler in Windows 64bit , Linux x86-64 Debian 11.1
Qt-6.2.1 everywhere opensource prebuilt binaries for win64 and amd64 are included into AdaStudio-2021
VTK-9.1.0 opensource prebuilt binaries for win64 and amd64 are included into AdaStudio-2021
AdaStudio-2021 includes next modules : qt6ada,vtkada,qt6avada,qt6cvada(with face recognition) and voice recognizer.
Qt6Ada is built under  GNU LGPLv3 license https://www.gnu.org/licenses/lgpl-3.0.html.
Qt6Ada modules for Windows, Linux (Unix) are available from
Google drive https://drive.google.com/drive/folders/0B2QuZLoe-yiPbmNQRl83M1dTRVE?resourcekey=0-b-M35gZhynB6-LOQww33Tg&usp=sharing
It can be mounted as virtual drive with ExpandDrive (https://www.expandrive..com/download-expandrive/)), go to Adastudio directory and load index.html to browser.
Directories tree is
AdaStudio - root
qt6ada - qt6ada components
qt-6.2.1win64.tar.bz2 - Qt-6.2.1 win64 prebuilt
qt-6.2.1amd64.tar.bz2 - Qt-6.2.1 x86-64 prebuilt
qt6adademos.tar.bz2 - qt6ada demos
qt6adasrc.tar.bz2 - qt6ada packages
qt6adawin64.tar.bz2 - qt6ada win64 binaries
qt6adax86-64.tar.bz2 - qt6ada x86-64 binaries

qtavada - qt6avada components
qt5avadasrc.tar.bz2 - qt6avada packages(qt5avada packages)
qt6avadademos.tar.bz2 - qt6avada demos
qt6avadawin64.tar.bz2 - qt6avada win64 binaries
qt6avadax86-64.tar.bz2 - qt6avada win64 binaries

qtopencvada - qt6opencvada components
opencv_4.5.2.win64.tar.bz2 - OpenCV 4.5.2 win64 prebuilt
opencv_4.5.2.x86-64.tar.bz2 - OpenCV 4.5.2 x86-64 prebuilt
qt6opencvadademos.tar.bz2 - qt6opencvada demos
qt6opencvadasrc.tar.bz2 - qt6opencvada packages
qt6opencvadawin64.tar.bz2 - qt6opencvada win64 binaries
qt6opencvadax86-64.tar.bz2 - qt6opencvada x86-64 binaries

voicerecognizer - qt6ada voicerecognizer components
qt6speech2textwin64.tar.bz2 - qt6voicerecognizerada win64 binries
qt6speech2textx86-64.tar.bz2 - qt6voicerecognizerada x86-64 binries
speech2textdemo.tar.bz2 - qt6voicerecognizerada demos
speech2textsrc.tar.bz2 - qt6voicerecognizerada packages

vtkada - vtk6ada componenets
vtk-9.1.0.win64.tar.bz2 - VTK 9.1.0 win64 prebuilt
vtk9.1.0.amd64.tar.bz2 - VTK 9.1.0 x86-64 prebuilt
usrlocallib additional modules prebuilt(x86-64)
vtkadademo.tar.bz2 - vtkada demos
vtkadasrc.tar.bz2 - vtkada packages
vtkadawin64.tar.bz2 - vtkada win64 binaries
vtkadax86-64.tar.bz2 - vtkada x86-64 binaries

The full list of released classes is in "Qt6 classes to Qt6Ada packages relation table.pdf"
The simple manual how to build Qt6Ada application can be readed in "How to use Qt6ada.pdf"  
If you have any problems or questions, tell me know.
Leonid(leonid.dulman@gmail.com)