I’ve had the same exact issue with my 2019 Blazer RS. I’ve been dealing with the dealership for a year now on this problem. Every time I take it in they tell me something different, fix something weird and then send me on my way. When I drive the car off the lot, the noise is instantly back. I’ve noticed that the issue only ever happens once the car comes to a complete stop, engages in the auto stop, and then the noise happens when the car starts and I accelerate again.
The first time I took my blazer into the dealership they told me I had a broken baffle. They fixed that and had me pick up my car. Noise still existed.
The second time I brought it in, they told me nothing was wrong and that the computer/sensors were not indicating any issue on the car. Noise still existed.
the third time I took the car in I had the tech drive in the car with me to verify that he also heard the noise. They confirmed that noise wasn’t supposed to be happening, and eventually replaced the entire exhaust system. This fixed the issue for several months until this past week.
the fourth time I took my car in to have it looked at they found a broken shifter cable and told me that’s causing the noise. Picked up my car today and the noise is still there.
I’m at a loss here, and maybe it’s time to just accept the annoying sound.