https://kotlinlang.org/docs/reference/multiplatform.html

I've also done multi platform recently.

I've taken a contract first approach. Swagger / openapi for rest clients. Outside of that I use vertx which has bindings for almost every platform. With those two I can account for interoperability across all platforms.

Big hitches

* No ts.d defintions at this time. But: https://github.com/vojtechhabarta/typescript-generator

* Dukat for automatic typescript definition importing (beta) https://github.com/Kotlin/dukat

* I've not done LLVM iOS. But I've read of some generic issues.

They are improving dependency management to handle multi platform. I can't find a link but it was on their blog