Per https://nodesource.com/blog/understanding-the-buffer-deprecation-in-node-js-10/, "improper usage of the Buffer constructor is still a path to insecure code inside an application".
I just followed the guide and got the logs coming over from CloudWatch to Scalyr, but this deprecation warning looks serious enough that I looked into a patch.
I have a PR ready, it's a very simple change to fix the issue but you should also update the .zip release.