How do I unlock my phone using a USB Keyboard?

I have an iPhone 6s Plus that I'm trying to unlock so I can create a backup using iTunes. However, it has a screen that does not respond to touch. I've tried performing a screen replacement, which did not resolve the issue. I have a lightning to USB-A adapter that I'm using to connect a USB keyboard, but the iPhone doesn't recognize it and the keyboard does not function. I tried the same setup but on my personal iPhone 7 Plus where it worked flawlessly. What should I do?