UltraVNC is easy to use and free software that can display the screen of another computer (via the Internet or a local network) on your own screen. The program allows you to use your mouse and keyboard to control the other computer remotely.
Uses a raspberrypi and a solid-state relay to unlock the door. A node server running optionally elsewhere manages the users and serves the WebUI. (no affiliation to Ring which used to be called doorbot)