You can certainly get stateful components with Karax. Perhaps I am missing something but Karax itself doesn't need any special support for them.
In the code for NimForum I've laid out each component as a stateful component, one example is the `threadlist` module: https://github.com/nim-lang/nimforum/blob/master/src/fronten.... You can see the `State` type defined there and all components follow this convention.