With something like Elixir/Erlang, the distributed system is quite robust and reliable from my experience. A bit rigid and somewhat difficult to configure for custom topologies, but dependable overall.

>a plain-old set of services talking via a message-broker

That said, I think you're absolutely right with distributed Akka. I'm very hesitant to fully embrace it, and we use simple service-level APIs to communicate between nodes. I understand the developers have made a lot of progress on the functionality of remote Akka over the years, but it's just not as tried and true as I would like. Using Aeron for message transport for example, is something that may be the best tool available, but is really hard to sell to my org when simple services are more approachable and maintainable.

>actors "becoming" (the term used IIRC) other types of actors based on messages received

Yeah... I didn't understand why my org was using the Classic Akka instead of the new and improved Typed Akka for a long time. But cool-looking things like this just aren't worth it sometimes. Especially when Classic Akka "just works".