I'm really glad I found this site and this thread. I recently picked up a 21 Sierra 1500 LT with the 3.0 babymax. I have 2k on the odometer and had my first crank/no start event last night.
It makes me very leery due to my last experience owning a Sierra. I had a 2016 1500 Denali that the dealership had for two months due to a 8-speed tranny replacement. I had to fight GM tooth and nail to get any help on that whatsoever. The bad tranny was after I replaced the A/C condenser coil, the starter (twice), vacuum pump, and both front magneride struts on a truck with less than 70k on the odometer. Before that I had a 2015 1500 with a litany of issues also.
Depending on how bad this crank/no start issue ends up being, this may very well be the that GM vehicle I own.