For existing Amazon Inspector customers using a single account, you can enable agentless scanning (preview) by visiting the account management page within the Amazon Inspector console or using APIs.
For existing Amazon Inspector customers using AWS Organizations, your Delegated Admin needs to either completely migrate the entire organization to an agentless solution or continue using the SSM agent-based solution exclusively. You can change the scan mode  configuration from the EC2 settings page in the console or through APIs.
For new Amazon Inspector customers, during the agentless scanning preview period, instances are scanned in agent-based scan mode when you enable EC2 scanning. You can switch to hybrid scan mode if needed. In the hybrid scan mode, Amazon Inspector relies on SSM Agents for application inventory collection to perform vulnerability assessments and automatically falls back on agentless scanning for instances that don’t have SSM Agents installed or configured.