I never tried this myself, but Gradle is only a build system and I don’t think it is anyhow required by the Kotlin. You can probably use Maven if you prefer or you can write your own scripts, makefiles or whatever and call kotlinc directly.

And what do you mean by saying IntelliJ doesn’t support its own build system for Kotlin? The below created a new Kotlin project without Gradle for me:

As long as you don’t target multiplatform, you can use maven and IntellijIdea will allow it. But multiplatform projects have to use gradle.

A developer tried to craft a new build system in pure kotlin, GitHub - cbeust/kobalt: A Kotlin-based build system for the JVM., which looked very promising, but alas the project isn’t maintained anymore.

Oh, how far the happy days of Makefile scripting seem…