If you can't find the new Slackers ark server in the Unofficial servers list, you need to add the IP address of the server manually to Steam.
Exit Ark and open your Steam client. In Steam, in the top Menu, go to View then Servers.
Go to the Favorites tab, then click the Add A Server button
Enter the IP address 184.108.40.206 and click Add This Address To Favorites
Finally, start up Ark again, and our new server should appear in your Favorites list (if it's online & version compatible).