The steps to enable the LeakHunter extension are documented here - https://techdocs.broadcom.com/us/en/ca-enterprise-software/it-operations-management/application-performance-management/20-2/implementing-agents/java-agent/advanced-instrumentation/configure-and-use-leakhunter/enable-leakhunter-in-the-agent.html however the feature does not appear to be included in the agent distribution.
Leakhunter is not intended for use in a production environment and so is not included by default in the agent downloads from the DX platform agent download dialogue.
Release : 20.2
Component : APM Agents
Leakhunter is still available but it will be necessary to create an agent package in APM Command Center and add the bundle to it.