Interfaces are not exportable.
Declaration of such kind (interface) cant be exported to JS
Only external interfaces are exportable. That means you have to copy-paste the interface from commonMain to all your specific module (androidMain, iosMain, iosSimulatorArm64, ...), mark the commonMain one as expect, all the other ones as actual and eventually the jsMain one can be marked external and receive the @JsExport annotation.
That's a bit tedious and very painful to update several files when changing the signature of one method.
Just mark the interface with @KustomExport and it's now available for typescript.
Internally it's generating a wrapper + 2 import/export methods so that all input/outputs can be mapped from typescript to kotlin types.