Vntage Story is pretty neat, it does require a WAN connection to start it for the first time but AFAIK it's possible to play it completely offline afterwards.
Beimg as mechanically complex as it is you'd think you need a wiki open the entire time, but the ingame "guide" has everything you need to know.
I don't know about the state of public multiplayer servers, but it is LAN compatible and it actively supports modding!