Dsalibu and PerryGT thank you for your interest.
In the meantime, I have done a little research.
I tested on Hololens 2:
1) Unity 2019.4.12 / MRTK 2.4 and Vuforia: 8.5.9, 8.6.10, 9.3.3, 9.4.6,
2) Unity 2018.4.28 / MRTK 2.4 and Vuforia: 8.3.8.
1) It all works with "Windows Mixed Reality" package (4.2.3/1.0.21) - with "Windows XR Plugin" it's not working (properly).
2) I used profile for Hololens2 but XRSDK also works.
3) XR rig is needless.
Directly using Vuforia samples failed but I created new project and used a part of the samples - content of folders:
4) Additionally on Unity 2018: Vuforia\Materials,Vuforia\Scripts, Vuforia\Shaders.
The "Device Tracker" option in the Vuforia configuration should be turned off and of course the "Vuforia Behaviour" script must be added to the "Main Camera".
I tested only the "Image Target Behaviour" with type: "Predefined" and "From Image".
Sometimes there was a problem with the model shift in relation to the recognized image, but in recent tests it has magically disappeared :)
It also works in the Unity editor, but models are transformed in relation to targets due to the use of the Main Camera matrix - the positions of the Webcam and the Main Camera do not coincide.