Revival servers are unofficial. They are rebuilt by reverse engineering, and none is endorsed by the company that owned the original platform. Most ship no game files and expect you to supply your own copy of the client. Whether running one is legal depends on where you live and is unsettled. We list them as facts, not recommendations, and give no setup instructions.
No server revival exists for AltspaceVR, Facebook Spaces, Oculus Venues or vTime XR.