Oracle Standard Edition 2 v19, License included, non-cdb to 21 CDB?

Amazon RDS supports Oracle Database 21c, which includes Oracle Enterprise Edition and Oracle Standard Edition Two and it supports only the multi tenant architecture. you must choose Amazon RDS with Multi tenant architecture while creating database and then you will see Oracle Standard Edition Two, license included option with 21c. RDS for Oracle major versions remain available at least until the end of support date for the corresponding Oracle Database release version. Before we ask that you upgrade to a newer major version and to help you plan, we provide a reminder at least 12 months in advance. We do so to communicate the detailed upgrade process. If Amazon extends support for an RDS for Oracle version for longer than originally stated, we plan to update the table to reflect the later date which can verified at: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_UpgradeDBInstance.Oracle.Overview.html