Relativty  – An open-source VR headset
The developers could add 6dof roomscale tracking relatively easily by adding an intel 265 (<a href="https://www.intelrealsense.com/tracking-camera-t265/" rel="nofollow">https://www.intelrealsense.com/tracking-camera-t265/</a>).  The unity integration is very plug and play.  The 261 can also be used but must be bought in trays of 8.