Tracking running usage instances and launch templates launched from shared AMIs in external accounts - is possible from the owner side?

Unfortunately, there is no AWS native way to track running instances and launch templates launched from your shared AMIs in external customer accounts without their cooperation or access to those accounts.

The AMI Usage feature does provide the ability to generate reports showing which AWS accounts are using your shared AMIs and how many resources (EC2 instances and launch templates) are referencing them. You can specify the AMI ID and the account IDs you want to report on, and the report will show the number of resources by resource type per account.

However, there are important limitations to be aware of:

1. The AMI usage reports are point-in-time snapshots and may not contain the most recent activity
2. The reports show resources that reference the AMI, but this doesn't necessarily mean those resources are currently running
3. You cannot get real-time or accurate counts of actively running instances in external accounts from the owner side alone

To get accurate, real-time information about running instances and active resources using your AMIs in external customer accounts, you would need cooperation from those accounts. They would need to either provide you with access or share that information with you through some other mechanism.

The AMI usage reports can give you visibility into which accounts are using your AMIs and approximate usage patterns, but they cannot provide the level of detail you're looking for regarding actively running resources in accounts you don't have access to.
Sources
View your AMI usage - Amazon Elastic Compute Cloud
Manage and monitor AMI usage - Amazon Elastic Compute Cloud
What's New at AWS - Cloud Innovation & News
create_image_usage_report - Boto3 1.42.50 documentation