I have an iPhone X that I was about to update with iOS 14 Beta 3. When I hit "Install Now" it said something to the effect of "an unknown error" occurred. After that, the phone literally won't launch any app, and the hardware buttons won't restart the phone (though they do still otherwise work for volume, etc). I can interact with Siri. If I say "Open Settings", Siri responds with "I couldn't Open Settings. Sorry about that". Basically, I need to figure out any way to interact with the phone short of waiting several hours for battery to drain or disassembling phone. Has anyone ever seen this? In 10+ years, this is a first for me.
I was able to resolve this. I didn't realize there was a new force restart sequence since the emergency all process took over the power/volume combo (which is what I'd been trying). New process was to:
Press and release the volume up button.
Press and release the volume down button.
Press and hold the side button until the screen turns off and then turns back on. You can release the side button when the Apple logo appears.
Press and release the volume up button.
Press and release the volume down button.
Press and hold the side button until the screen turns off and then turns back on. You can release the side button when the Apple logo appears.