Hibernating your Amazon EC2 Instances is now easier then ever. You can now enable Amazon Elastic Block Store (EBS) Encryption by Default, to ensure all new EBS volumes created in your account are encrypted. To enable Hibernation, you no longer have to create an encrypted copy of the Amazon Machine Image (AMI) before launching an instance. Alternatively, you can also now specify encryption intent at launch (with unencrypted AMI or snapshot) and enable hibernation at the same time (see link).  

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/05/enable-ec2-hibernation-without-specifying-encryption-intent/