My 2016 SSVR is a slapper
I describe it as being similar to the sound of a diesel engine, just not as loud.
There are countless online examples of Chevy LS engine owners with similar sounds emitting from their engine during cold startup. The slapping noise is due to the short piston skirts GM use on the LS series of engines which are designed to create more efficiency by reducing piston weight. In my case and many others, the noise fades away after the engine reaches operating temperature (which can take up to 10mins). The pistons expand when hot which tighten the clearances against the cylinders thus minimising piston slap. There are variances in each engine and apparently Chevy no longer measure piston clearances per cylinder so all it takes is one piston with a higher clearance to start slapping away.
As much as I don't like it, it seems to be normal for these engines. I don't recall my car having the noise when new so I think its something that develops over time. Pretty sure mine appeared after 10,000kms of City driving but I could be wrong and it was there all along.