The only reason you could have a problem using Immutable.js with redux-simple-router is if you're trying to make the router's state into an Immutable.js data structure, but there is no reason to do that. redux-simple-router manages it's own part of the state, and you don't need to directly mutate it. You only read it or dispatch an action to update it.
You don't need to make the entirety of your state tree an Immutable.js structure, just the parts which are managed by the reducers you write.
You don't need to make the entirety of your state tree an Immutable.js structure, just the parts which are managed by the reducers you write.