Android, IOS (with e.g. kmm, or compose multiplatform), browser (with kotlin-js and react, fritz2, kweb, or several other popular frameworks). Soon web assembly

Android, IOS (with e.g. kmm, or compose multiplatform), browser (with kotlin-js and react, fritz2, kweb, or several other popular frameworks). Soon web assembly. And there are of course lots of jvm based server projects that use some sort of asynchronous framework (Spring web flux, vert.x, netty, etc.) that you can use with co-routines as well. Basically everything except what you are doing with it. Nothing wrong with that, I've been on such projects too. Anyway, non blocking IO is pretty common in the jvm world these days. And most of that works great with co-routines. And of course most Kotlin users are still found on Android. Doing modern Android without co-routines is not a thing.