How to Turn Off Samsung S21 From the Notification Shade

The first method is found in the notification shade.

How to Turn Off Samsung S21 With the Power Button and Volume Down

You can still use the power button to turn off the phone. If you long-press the power and volume down button, you’ll get a menu that will allow you to turn off the phone. Tap Power off (or Restart, depending on what you want to do).

How to Turn Off Samsung S21 By Asking Bixby

Another alternative for powering off your phone is to press and hold the power button to summon Bixby. While pressing the power button, after the Bixby animation appears at the bottom of the phone, just say “Turn off my phone” then release the button. You’ll get a prompt asking you to Power off or Restart. Press the appropriate button. 

How to Turn Off Samsung S21 if the Phone is Frozen

Sometimes your phone can freeze and turn non-responsive. If that happens, all is not lost. Press and hold the power and volume down buttons for 15 seconds. Doing so will force the phone to restart and any issues should then be cleared up. Samsung’s power button now carries a lot of functions; arguably “power button” is a bit of a misnomer these days. Given the recent changes to the interface, this can cause some confusion, but any of these three methods will allow you to power your phone off.