AWS can host Oracle APEX!
AWS is the leader and the top of all cloud services provider. AWS can host your APEX 20.1 on Amazon RDS. For more information, please check the following link
However, , to the best of my knowledge, Oracle Autonomous Database (ADB) has great power of AI and ML. In the other hand, AWS does not have a product like ADB. That’s why I would prefer using Oracle ADB with APEX.
It worth to mention that AWS has an IDE used to build ML models called Amazon SageMaker. You could use Data from an Amazon RDS Database to Create an Amazon ML Datasource