Our three Beanstalks are currently running on the "Tomcat 8.5 with Java 8 running on 64bit Amazon Linux" platform, either on the canned "ami-0e469f970b0c3b65c" AMI, or (for one of them) on a customized version of that AMI with Java compilation capability added.
Creating a new Beanstalk with the platform "Tomcat 8.5 with Corretto [x] running on 64bit Amazon Linux 2" seems straightforward enough, but what do I do about the existing Beanstalks? Do I start from scratch, with new Beanstalks? Or is there a way to convert the existing ones?
I believe you have to create a new environment, and when it's working you can terminate the old one.
The docs don't say much, except
Blue/green deployment basically means that you'll switch your URL from the old environment to the new one once it's working and then you can terminate the old one.
We haven't done the migration ourselves yet, but that's how I understand it.