I am going through the exact same issue with my 21 Tahoe Premier. Did you have any luck solving the problem?
Diffidently time to update this thread.
The issues I was dealing with before, e.g. error codes, infotainment system no longer functional, etc. remained the same. It took almost 1 1/2 months to get into my local dealer, and then the truck sat at the dealer for another week before even being diagnosed but that's another story...
The entire problem was due to the failure of the Radio Control Module Part # 87836477, also called the radio receiver. According to the Chevy shop Foreman, this module controls numerous functions within the truck and when it fails will cause a series of communication failures.
Either way, receiver was replaced. I drove off lot and the infotainment system began rebooting, every few minutes. Sometime the reboot would occur every few minutes, sometimes it would go into a boot loop.
Here's a video I took >>
I turned around, right back to the dealer, and the foreman took a look and said radio control module, that was just replaced, would need to be replaced again. This occurred during the holidays so I had to wait another few weeks for the module to come in and get it replaced again. The system has been replaced and is functioning as normal. Crossing fingers.
I've never purchased an extended warranty except with this truck, I did so in case the lifter issue occurred. Thankfully I did as this would of cost $1143.90.
#87836477 Receiver = $752
Labor (2.3 hrs) = $391
According to my Service Advisor, he'd only been there for about 5 months and has already replaced 3x of these units. I hope this helps someone.