Unable to access phone after update to iOS 12.1.4
Connect your iPhone to iTunes


  If iPhone is locked, iTunes will not recognize that it's connected.


Therefore, you have to put your iPhone to DFU mode. Usually, a key combination is used to do that (requires home button).

Other way is to use third party software, which allows you to enter DFU mode with one click.


Recboot
Tiny Umbrella
Redsn0w



  I have not checked, whether second and third option works with your iOS and iPhone, but there are a few others worth trying.


When your iPhone enters DFU mode, you will be able to manually reinstall iOS using iTunes or recover from backup.