As a turing machine can compute anything that is computable it is therefore impossible for an Actor to do any computation that is not possible by a turing machine. This is computer science 101 and makes me wonder about the value of anything else said in the paper.

Of course it's sealed forever for a specific definition of 'compute,' but I'm still open to the idea that we find something which resembles computation enough that we call it the same thing, yet its precise definition is different enough from the one used in connection with contemporary theory of computation that old proofs of universality won't necessarily apply to it.

That said... it seems unlikely to me that the Actor model does something non-trivially beyond what Turing machines are capable of, since it would likely be better known, and we would see Chomsky's hierarchy expanded to hold another class, etc. (Unless it goes beyond Turing Machines by being non-linguistic in some way, which could certainly be interesting. Maybe dealing with non-sequential symbols or something?)

Message passing is fundamental for IoT, etc.

It is impossible for Actors implemented on a Turing machine to do anything that a Turing machine cannot. But the Actor model itself is larger than a Turing machine - eg nondeterminism.

Turing completeness is a lower bound on computation, not a maximum. For instance, a CPU with a hardware random number generator is a Turing machine, but a (basic/strict/pure) Turing machine cannot emulate a CPU with a hardware random number generator!

Another common misunderstanding is that an an Actor must have a mailbox, message queue, or event queue. There would be an infinite regress if any of these were required because since everything is an Actor, each of these would itself need a mailbox, message queue, or event queue!

[1] Carl Hewitt; Peter Bishop & Richard Steiger (1973). "A Universal Modular Actor Formalism for Artificial Intelligence". IJCAI.