How to Find EBS Volumes Attached to Powered Off EC2 Instances Across Multiple AWS Accounts?

You might want to check out Steampipe! It's a great tool that lets you write SQL-like queries against AWS APIs, and it can handle multiple accounts at once. That way, you could run a single query to find what you need across all your environments.

If I remember correctly, you can look for stopped instances and then identify the volumes attached to them. Alternatively, you could list all your volumes and then check which instances they're attached to, and see if those are stopped. The CLI or Boto3 should make this pretty efficient.