I used Nova Launcher double tap gesture to turn off screen, with Android Pie it is possible to use Accessibility locking method that support fingerprint unlock.
So I basically double tap to lock screen and fingerprint to unlock, and have a Floating Bar V40 app for screenshot, power off & restart device. Hardly press the power button once.
P3 do have double tap to 'wake' (check phone) under Settings > System > Gestures (and also under Settings > Display > advance > Ambient Display).
This
Double Tap Screen On and Off also support Accessibility services on Android 9 for turning off the screen, but I found it not as reliable as Nova's double tap gesture.