Kotlin is the future of multi-platform languages. It is officially supported by Google for Android App development and it is also an alternative for backend development as it runs on the JVM.
Beyond backend development, frontend development can be done with Kotlin JS and, thanks to the Kotlin Native project, Kotlin could be seen in a short term running in any device; from Raspberri Pi to iPhone.
What does this mean? With the skills you will learn in this course you could develop functional software in any platform and even be able to share code between them.
Kotlin is here to stay and its easiness and functional capabilities make it the perfect language to begin with functional programming.