I’ve never used any system to migrate apps between platforms. I code them natively if needed, adjusting UI/UX as expected between platforms.
Having said this, for what I’ve heard in a conference where some guys from Apportable explained. They are slowly building up their system. But, as you can imagine, it’s not that easy. On the other hand, it’s straightforward to migrate from OpenGL to OpenGL, doesn’t matter the platform. And that’s the reason why games are widely supported, not only by Apportable but for many other cross-platforms.
If you ask me, my option would be to learn a bit of Android (once you know iOS, the basic knowledge of Android is peanuts), and code it. For simple apps, you can do it really fast.
solved Run xcode ios project on Android