On my 2015, I followed the camera cable up to an electrical box under the bed, on the plug there is a red lock tab that you slide back, then depress the tab on the plug and it should disconnect. There is a dummy plug stored next to the camera plug that you use to protect the open connection. Good luck.
"This" .....exactly same on my 2016 GMC 3500....
IMHO any year GMC is probably closer in design to a 2019 than a Ford or Dodge....this stupid type of posting seen here is why this forum is dying... helpful posters are not much inclined to stay here to be ridiculed by idiots.