This is pretty much a lab around Orleans StreamProvider API, as EventStore does not fit well in Orleans StreamProvider model, which is a queue management API.
One other attempt (.NET Framework and Orleans 1.5).
Some StreamProvider implementations, as the documentation is really scarce on the subject:
https://github.com/jonathansant/Orleans.Streams.Kafka
https://github.com/galamai/Galamai.Orleans.Streaming.RabbitMQ