Nim is first and foremost a procedural language like Go, if you use it as a better Go you'll have a great time, if you try to make Nim more OOP you can use libraries like: https://github.com/bluenote10/oop_utils to make it easier.

Besides that Nim uses UFCS, you can mimic 90% of your OOP needs without using pragmas or methods or anything like that.