Seeking Guidance on Migrating CentOS 7 EC2 Instances to Amazon Linux without Downtime

For guidance about CentOS alternatives, you can refer to CentOS End of Life Guidance

As per that page, Binary/ABI compatible options include RHEL, Rocky Linux, Alma Linux and others.

If you choose RHEL, you can refer to Leapfrog from CentOS 7.9 to Red Hat Enterprise Linux 8.9 with Convert2RHEL and Leapp Utilities on AWS for the steps

Else, you can consider using ELevate to do in-place upgrade from CentOS 7.x to say Rocky Linux 8.

The in-place upgrade will take some time and may not succeed. To minimize downtime, you can consider using AWS Application Migration Service (AWS MGN) to migrate EC2 to another EC2. MGN uses a replication agent to do continuous replication from source EC2. MGN supports test instances for testing your migration, so you can launch a test instance and test out ELevate. If successful, launch cutover instance and upgrade to Rocky with ELevate to complete migration.