can Kotlin actors be orchestrated in some kind of a hierarchy, possibly with restarts, stopping all descendent actors when a parent stops, etc..?

Kotlin doesn’t really (yet) have a full-fledged actors library, afaik. It has the

actor

function which is just shorthand for creating a channel and a coroutine to read from it – it doesn’t have all the features of most actor-based programming frameworks. That said, you can do anything with it that you could otherwise do with coroutine job hierarchies and other coroutine tools.