Good day,
Not sure if anyone is following this topic still however I had a very similar noise on the drivers side of my 2018 Yukon with 5.3. They changed the oil pump and the fuel lines (fuel line has a check valve that sometimes rattles) and on the 3rd visit to the shop the Tech started taking parts off and going for a drive to check for noise. He discovered it was the heat shield on the drivers side exhaust manifold that was making the noise. I took it for a drive while the shield was off and yep no noise anymore. He is putting back the heat shield and ordering a new which he'll change once in. So if the new one rattles then I will up date this post later but for now looks like my mystery is solved.
