Javascript is generally considered OOP, but classes weren’t widely available till 2017.

Inheritance isn’t fundamental to OOP, and neither are interfaces. You can have a duck- typed OOP language without inheritance, although I don’t know of any off the top of my head.

Honestly, the more fundamental thing about OOP is that it’s a programming style built around objects. Sometimes OO languages are class based, or duck typing based, etc. But you’ll always have your data carrying around it’s behavior at runtime.