How best to get the device name after receiving a message?

Again, nothing changed. But if you read the messages posted over the last week you will notice a forum user posted a GitHub issue regarding this. And that might be implemented (or not) to resolve your issue.
However don’t hold your breath because it will require more resources on the TTN servers which will result in larger VMs which are more expensive. So from view of the party paying for all the freely available (to us) resources it might not be something they want.
What is scalable for you might not be so for the operators of the stack…

Good to know.