Iphone dead after entering DF mode

Well, you have asked us to guess what “the problem with Face ID” might be.

I will take one guess. See this article.

If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support

If this version of the above article does not point you to Apple Support, then there would be no solution in your country. If the link to contact Apple Support functions, that’s your solution.

If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support

See this article.

If the Restore screen appears on your iPhone, iPad, or iPod touch - Apple Support

1. Check the Cable and Connection: Ensure that you are using a genuine and functioning USB cable. Try connecting your phone to a different USB port on your computer, as well as using a different computer if possible.
2. Restart Computer: Sometimes, restarting your computer can help refresh the USB ports and connections. Give this a try before proceeding further.
3. Force Restart Phone: If your phone is unresponsive, try performing a force restart. For most iPhones, you can do this by quickly pressing and releasing the Volume Up button, then quickly pressing and releasing the Volume Down button, and finally, pressing and holding the Side (or Power) button until you see the Apple logo. This might bring your phone back to a responsive state.
4. Check iTunes/Finder: If you're using a Mac with macOS Catalina or later, or a PC with iTunes, make sure your computer recognizes the device when connected. If iTunes/Finder detects your device, it might prompt you to update or restore the phone.
5. Try Another Cable and Computer: If your current setup isn't working, try using a different USB cable and connecting to another computer. This can help isolate whether the issue is with the phone, cable, or computer.
6. Contact Apple Support: If none of the above steps work, it's advisable to reach out to Apple Support or visit an Apple Store. They can provide more specific guidance and assistance based on your situation.