I wanted something like this a while ago. Most screen casting protocols like chromecast or airplay require a wifi network. If the truck itself doesn’t have wifi then it needs to be tethered to a phone. The issue is the phone used for the wifi signal cannot be the source for casting. In the end my kids prefer using their tablets.
My Denali doesn’t have rear entertainment but it does have Carplay. I have an AI box I use to stream whatever I want (YouTube, Netflix, Plex etc) to the main dash screen up front and it’s pretty awesome. I just added a SIM card to my account for ten dollars a month to share internet on my plan and it’s got its own independent 4G connection. It was only a few hundred dollars. Plus now it’s wireless CarPlay so I just use a magsafe charger or the wireless charger in the arm rest. That one rarely as it doesn’t work with my phone case.