Google Pixel and Samsung phones have taken over power menus by forcing Assistant and Bixby on you. You can change them back to power menus.

Quick Answer: To restart your iPhone without the power button, go to Settings > General > Shut Down, then slide to power off.

Phone manufacturers: please give us the power button back I don’t want to talk to Siri, Google, or Bixby. Please just make the power button do what it’s supposed to do.

Eventually, I discovered that I could double-press the power button to launch the camera on my Samsung phone. It also works on Google Pixel phones and other devices.