Loud knock when I start the engine

Possible cam phaser noise until oil pressure builds up.

sounds to me like a main bering, there are many test's you can do we used to get the car or truck put the bumper touching a pole and gently give a little gas and if it is a main you would hear it start to get loud so you can hear it again do not get crazy and try lots of gas, you could make damage to your truck, or the pole just want to all a bit of load