My impression after going to a meetup where they introduced Mantra is that you don’t use them together. Mantra has a parallel concept as what react-redux has for making container components that gets the store/dispatch and pass props/callbacks to a wrapped presentation component.
I don’t see the benefit of using both.
However, what was interesting was that in that talk, I asked the guy how he was going to test his container component because it has tracker, meteor.call and a whole lot of other injected modules that fire off at random times. He said he didn’t test that part, which was the most complicated area and prone to logic failures.
In contrast, just using Redux, I’m able to test 90% of my client side logic because they are mostly pure functions. The parts I don’t test are the trivial bits of wiring between third party components etc. I talk about my redux/testing workflow and it’s giving me some serious benefits to how I’m working.
EDIT: Just read the OP again re domain/ui state and I have alot more experience now to have a bad feeling about this. Redux is great because it keeps state simple and it keeps component updating efficient. Having another state which sometimes may be used by the react components is a bad idea, what happens if this domain state changes? Do you fire off a action to update the redux state? Why not just update the redux state in the first place.