The Problem

Strings in the iOS Device Log appear masked as <private> instead of useful information, eg:

SomeAppWhichYou'reTesting(BeepBoop)[244]: <private>

The Cause

This is a deliberate Apple feature; Any string variable that isn't declared public is masked in this fashion.

See https://developer.apple.com/documentation/os/logging/generating_log_messages_from_your_code?language=objc for reference and https://stackoverflow.com/questions/45908875/apple-iphone-debugging-with-console-private for more information

Workarounds

That Stack Overflow article links to a workaround using a C++ application to allow you to change an otherwise Apple-Internal value, revealing that log data.

This needs to be done by the app developer at compile time; We're unable to do so when deploying your app.  This also means it's not possible for built in and system apps.