One Steam feature isn't supported by Blockland and the other Blockland feature isn't set up properly with Steam.
-Family Sharing is entirely nonfunctional. It goes into demo mode. Not sure how this'd be fixed.
-Dedicated servers can only be hosted on the same machine as the client so you can't dedicate a machine to the server. A separate process marked as a server would fix this I think? Not sure.
There's not really a workaround for either of these as far as I know.