[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".

[zerocrates]

On my 9 you get a setting to choose if holding Power gets you the power menu or activates the assistant (I think it defaulted to assistant? I have it set to the power menu because I don't really ever use the assistant.)