@Joost Klitsie I think StateFlow is more a technical thing, whereas redux is a whole architecture pattern. You could even combine them.
Redux contains, besides the appState, reducers, middlewares and actions.
I think redux in a KMM setup forces you to put much logic into the shared module. Further, in a team of android and iOS developers, it creates a common understanding of how and where logic should happen.
Off course, you can achieve all that without using redux.