[regenschutz]

Sad, neither of those works on Android. Pressing the power button activates the emergency call screen with a countdown to call emergency services, and power + volume either just takes a screenshot or enables vibrations/haptics depending on which volume button you press.

[thallium205]

On Pixel phones, Power + Volume Up retrieves a menu where you can select "Lockdown".

[rationalist]

Not on my Pixel phone, that just sets it to vibrate instead of ring. Holding down the power button retrieves a menu where you can select "Lockdown".

[silisili]

Did you check your phone settings? Mine has an option to add it to the power menu, so you get to it by whichever method you use to do that (which itself is sad that phones are starting to differ in what the power key does).