In my case subprojects references are not resolved, and the build script for the root project returns errors such as "can't find implementation". Pretty strange. I'll try the same with a non kts script.

Although the player:build command is now giving a different error, 'Execution failed for task ':kotlinNpmInstall'.

Cannot find webpack@4.41.2 in yarn.lock'

Yeah these errors don't give me a good sense of how to fix them

I tried upgrading yarn to the latest (1.22.4), didn't help

It seems that the included project doesn't search in any of the repositories I specify in the buildScript node, whether that be in the root's build file or the project's build file. Seems like it could be a bug?

This is causing some plugins to not be found, and also it seems that the classpaths specified are not being applied, also causing some of the plugins to not be found because they don't have the version specified on the classpath