The "VIVE OpenXR Plugin" plugin package contains some OpenXR Unity features for developers to use.

https://github.com/ViveSoftware/VIVE-OpenXR/blob/master/Installer/ViveOpenXRInstaller.unitypackage

Note: For "Install specific version", please copy the release version from https://github.com/ViveSoftware/VIVE-OpenXR/releases, then paste the version(for example: "1.0.12") to install the specific version.