I also faced print issues when running flutter app in iOS. There is a way that you can get all the log of the device using Xcode.

you should open like, Xcode -> window -> Devices and simulators -> select your device you're running -> Open console

this will open a window that will show whole log of the device and you can filter it with any keyword, even you can check keyword like contains, not-contain, equal and no-equal etc.