iPhone owners: your phone has an invisible button on its back.
go to Settings > Accessibility > Touch > Back Tap. you'll see two options: Double Tap and Triple Tap. assign each one an action: screenshot, Control Center, flashlight-style shortcuts, mute, scroll, or even a Shortcuts automation.
now tap the back of your iPhone twice (or three times) with a finger. the action happens instantly. I set double tap to screenshot and triple tap to open the camera via a Shortcut. it works through most cases too 👍 its available on iPhone 8 and later with iOS 14 or newer.
