Take a look at the 'Version' dropdown found on the Downloads page (See screenshot below) for available downloads: https://download.appdynamics.com/download/
As mentioned previously, it is not recommended to be on a controller version lower than v4.4.1. You may also consult the product annoucements page for release notes for further details on versions available.
Lastly, receive notifications for the latest AppDynamics release.
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