How to configure multiplatform plugin's yarn download URL


I am migrating a project from the old kotlin platform plugin + node plugin to the kotlin multiplatform plugin (1.3.70).

The project builds a backend based on Ktor plus several web frontends using the JS target.

I am facing problems because we are behind a corporate firewall and the build fails to download the nodejs distribution and the yarn distribution.

I succeded in configuring where the plugin will download nodejs from by adding a kotlinNodeJs block to my buld:

kotlin {
    js {
        browser {
            kotlinNodeJs {
                // download = true
                // nodeVersion = "12.14.0"
                nodeDownloadBaseUrl = "<alternate download location accessible within my organisation"

Unfortunately I cant find a way to do the same for the yarn location. Looking at the kotlin-gradle-plugin source code I saw it seems to be possible (through a kotlinYarn block) to configure it but I have not been successful.

Any idea how to do that?