I have to describe owners of certain properties and those can be persons or companies. I was thinking of naming them entities, but that seems too broad.
I don't think anything other than owner could better describe this. Other words would be confusing and strange to the readers of your text. I think your misconception comes from the idea that owner can only refer to a person or a human being, but that's not the case. For example, you can say that the owner of this property is Microsoft or Apple and everybody will understand what you mean. Here are some more examples that may help you better understand the usage of owner.
"Microsoft is the owner of Windows 95, Windows 98, Windows NT, Windows 2000 and Visual Basic."
Apple is the owner of iPhone.
Mike is the owner of this website, place, shop, etc.