Vintage Story comes with a land claiming system that lets players protect their valuable resources and structures. Introduced in version 1.6 it is as of to date unfortunately only available through typing a sequence of commands as documented on the List of multiplayer commands.
It works by creating a new claim, adding one ore more cuboidal areas to the claim and then saving it. The owner may also grant use or build access to other players. Be aware though that there are limits on how much land you can claim. By default it is 4 chunks and up to 3 non-adjacent areas, but these values may greatly value from server to server. You can use the command /mystats to see how much land you can claim.