We’ve made an update to Chains of Domination today.
Previously on the PTR, only newly-created Shadowlands Legendaries were set to receive a gem socket. With today’s update, all items granted legendary power by the Runecarver in the Helm, Neck, Bracer, Belt, and Ring slots will receive a socket, whether you’re creating a brand new item or upgrading an older one.
We’re working on an issue with this: the preview of some items may not show the socket when you’re setting up your upgrade at the Runecarver, but the socket will be included on the final item. We’ll get the preview fixed as soon as possible.