Viele Dank für die Antworten.
Diese Plugin Vielfalt verwirrt mich einwenig
https://docs.unity3d.com/Manual/XR.html
Note: Valve and Google have used Unity’s XR SDK to develop their own plug-ins for OpenVR and Cardboard, respectively. These plug-ins are compatible with Unity 2019.3 and later. For more information, see the Getting started with VR development page.
https://forum.unity.com/threads/when-unity-xr-will-support-steamvr.1001044/