iPhone 6s smashed screen and appears dead, no sound, no vibration

Hi I have a 6s that I was recently given by a freind. The phone has a smashed screen that doesnt do anything. it initially appears dead but will appear in itunes and I can call the phone and hear it ringing on another phone.

It wont vibrate when called or mute switch toggled. power button doesn’t work so will only power up when it is plugged in. I cannot answer a call through a headset nor hear anything.

Im considering buying the parts to fix the phone but is there any chance that there is something wrong with the logic board to stop all these functions from working?

Thanks