I have the same exact problem with my 2020 Chevy Silverado 2500. It did not make the this noise when I bought it. Then after taking it to the dealer for another issue, The service rep mentioned a TSB regarding improper torque on my leave springs. They go ahead and retorque and all of sudden I have the noise.
CHEVROLET TSB #20NA022
2020 CHEVROLET SILVERADO 2500