Kotlin has a major benefactor in Jetbrains, buy they are also a major gate keeper with no interest in adding support for anything but IntelliJ. Quite to the contrary, they are actively blocking extensions to their compiler API that would improve development of open language servers.
If you want to develop in Kotlin, you should really just stick with IntelliJ. Or make your peace with not having the greatest language support in your editor.
Honestly, because of the whole situation, I've started considering Kotlin as a proprietary product by now.