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.
Release : 20.2
Component : APM Agents
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.
Leakhunter is still available but it will be necessary to create an agent package in APM Command Center and add the bundle to it.