Samsung How to Turn On/Off Bixby launch on Power button

Before Bixby, the Samsung device could be turned off using the familiar on/off button, but pressing and holding the power button (Samsung now calls it a function key) will start Bixby. Turning off is now done via the status bar or by pressing the power and silent key combination.

If you want the usual way of turning off the Samsung device, you can deactivate Bixby on the on/off button, which will open the menu for turning off, restarting or emergency mode as usual.