Is there a way to verify if the data used by Installed Apps goes to a different service or if it is rather all processed within Salesforce frameworks? Looking to see whether installing a Salesforce Labs App is an option or not.
Any Lab which does not request a "Remote Site Setting" would be running on the native platform. I am not familiar with any such labs that do have Remote Site Settings, but it would be obvious during installation if any such settings exist (the platform will ask you to allow/deny any such settings on installation).
Additionally, when installing third party apps (such as ours, since i work for an isv) we are obligated to disclaim external service providers used alongside ours that are used, this does not mean that the service is NOT HIPAA compliant, you still have to validate that those services are HIPPA. Additionally, some service providers offer both, Hippa and non hippa compliant services, so you might have to do your due diligence.