I'm ready to confirm the symptoms that Haiku has. I've also tried all of the mentioned advices and their combinations and none of them helped. I'm still switching layouts by mouse through flag icon clicking,- and that is awfully inconvenient.
What's more interesting is that I had layout switching previously, but probably after updates something became broken. One thing to add, is unability to have different layouts in separate programs, it is the same everywhere and setting "Allow different layouts for individual windows" option doesn't work.
That's a pity as I can't use Manjaro Cinnamon edition at work productively.