i personally love dwarf fort, terraria and rimworld (iv not played rimworld a ton but i still love it) those not mmo so prob not interested (thou can play terraria online if you try
then theres project zomboid mostly offline and in devlopment and thay are growing thier team latly by alot but iv had a ton of fun on some servers and its prob my fav building game outside dwarf fort and haven and im excited to see what thay do with it
as for mmo sandbox games that fit thay are rare or dont even compare to haven
iv been waiting to try samutale thou im not sure about it
before i found haven i use to play online miecraft servers it acually plays alot like haven on some of them (mabye even some were inspired by it who knows as theres always new ones poping up but the big ones tend to stay around a longtime)