https://www.pcgamer.com/multiplayer-skyrim-together-mod-is-now-in-closed-beta/

Skyrim’s NPC companions aren’t very useful, but if you still want company on your mountain hikes and dragon-slaying adventures, Skyrim Together might scratch the itch. Following the announcement earlier this month, a closed beta is now available for Patreon backers. It’s expected to run for a week or two, building up to an open beta. 

In the closed beta, players will be able to invite friends into their game and start private sessions, fight each other, travel wherever they want—separately or together—and join each other in quests. You can read the list of features on the subreddit. And here's a list of planned features.