TextEdit

Summary
TextEdit is an app that is present on all newer InternalUI builds. It was first spotted in a supposed leaked screenshot of iOS 8 posted to an unknown Weibo account back in March of 2014, and later reported on by 9to5mac and other sources. It has been spotted several times since, including back in 2016 when it was spotted on the Home Screen the presenter's iPad during the "What's New in Metal, Part 1" session at WWDC. TextEdit serves the same purpose on iOS as it does on the Mac, that being to read and write Rich Text Format (RTF) files, along with several other plaintext formats. TextEdit is linked to the Files app and can create and save files to iCloud Drive from within the app. Due to its simplicity, TextEdit does not depend on any special PrivateFrameworks from the InternalUI build itself, meaning it can be sideloaded onto production iOS and should run just fine without any problems.