I have used MacRuby (what RubyMotion became) and I quite enjoyed it - I made a small app and put it on the Mac App Store and was surprised by how many bought it (I priced it at the cheapest level, which is/was 99p here in the UK). I haven’t used it for mobile apps but I’d expect the experience to be fairly similar.

So it means RubyMotion is a mature technology.

Yes.
I wish Microsoft buys it the way they bought Xamarin and open sourced it.