Cr Lloyd

I read recently (3/31/21) there was an update (v155) to the infotainment on the 2021 Sierra that for now, only dealers can manually update. I have hear of at least one more update prior. When my truck was at the dealership for something else, they said there were no updates to apply. If I click "about" in the settings menu, it says the software build is March 2020. When showing the "update history" below that, it shows nothing. Every time I try to do an OTA update, it doesn't find anything. Does my dealership just not know? Lastly - I am a tech guy. I can't find anything on previous updates, release notes, etc. ?