The experimental branch has been uploaded to steam, this does indeed include multiplayer.
You will need to run your own server at this moment, our dedicated servers are still being set up. Your server will show up on a master list of servers for others to see and join. Running headless servers will soon be in place.
To download experimental, go to your library and right click on Age of Survival, navigate to settings and the Betas tab. You should see an experimental branch to switch to and download there.
Please take note this is extremely early and experimental at this moment, hence the experimental branch. Bugs do exist, we know, we are working on them daily.