Although at the time of this post we are not 100% sure if MySQL 8 is officially supported by Magento, however, we are now offering the MySQL 8 engine as a choice with our new version 1.4 of our Magento 2.3.2 : aMiSTACX S3 Titanium G4 LAP stack.
Just select MySQL 8 as part of the RDS engine choice during CFT deployment. Initial testing proves no major errors or problems, and slight performance improvement out-of-the-box.
We love to stay ahead of the curve, and even have PHP 7.3 on our stacks. So MySQL 8 as a choice to be used in development or for testing, or for production [when officially supported] just is the aMiSTACX way of Better Stronger Faster!