In addition to today’s update, Apple has restored group FaceTime to its original functionality. However, in order to use the feature, you’ll have to be running iOS 12.1.4. So if you and your friends like to have group video chats often, make sure you remind them they have to be on version 12.1.4 moving forward.
To install the update, head to Settings > General > Software Update. So long as the software has reached your device, you should see the option to download and install it. Be sure to have plenty of power left and a stable Wi-Fi connection to avoid any interruptions during the process.