Most of the delay I have been seeing is sitting in port(s). I believe several other folks have seen this. My dealer has been super responsive, and the emails from GM have actually been pretty good lately. I'm assuming my dealership set me up for this.
Truck has been sitting in Baltimore (I'm in VA) since ~5/17. The dealer has told me they are expecting it soon, but they are taking everything they hear with a grain of salt as truck drivers to deliver these things are in a huge shortage.
Built in early April, sat in Mexico for 3-4 weeks, now sitting in port for 3+ weeks.
I'm sure if GM could wrap these things up in a cardboard box and ship them UPS, they would
Also, I'm not sure if you all have seen the same thing... but Fedex has been really bad the last couple years. They are catching up a little in the last few months, but for a while there I just assumed anything sent Fedex was going to be delayed like 1-5 days.