Catalina: Instruments with Full Disk Access

I have the same issues. Updated MAMP to the latest build (5.5). Also switched the ports back to MAMP default ports (8888). That worked for me. Also checked if some diffrent server was running on port 80 lsof -nP -i4TCP:80 | grep LISTEN but nothing seem to be using port 80. Could it be Catalina has a new security setting for this?

The System Preferences screen is a bit vague (it says "Allows specified apps access to data like Mail, Messages, Safari, Home, Time Machine backups, and certain administrative settings for all users on this Mac.")

However the Apple developer documentation is more explicit - it says Full Disk Access (SystemPolicyAllFiles) covers all protected file locations including the new ones you mention. From PrivacyPreferencesPolicyControl.Services :

SystemPolicyAllFiles Allows the application access to all protected files, including system administration files.

More fine-grained file locations are listed in the link, including those you asked about. Specifically :

SystemPolicyDesktopFolder Allows the application to access files in the user's Documents folder.

SystemPolicyDocumentsFolder Allows the application to access files in the user's Downloads folder.

SystemPolicyNetworkVolumes Allows the application to access files on network volumes.

SystemPolicyRemovableVolumes Allows the application to access files on removable volumes.

Note that PrivacyPreferencesPolicyControl says "In the case of conflicting specifications, the most restrictive setting (deny) is used" but it doesn't seem to be possible to grant Full Disk Access and revoke another permission in Files and Folders through System Preferences.