I recently blogged about the developer experience with server-side Kotlin at https://glennengstrand.info/software/coding/csharp/kotlin so you should know that the IntelliJ folks offer a community edition of their IDE that works great with Kotlin. You don't even need the IntelliJ IDE at all. I was able to code up that Kotlin service using VS Code which was also a great experience. Nothing felt limited or dummied down at all.