It was definitely the water pump (not the thermostat) on mine -- the dealer was able to see it with a borescope. While the pumps are on national backorder for 45+ days, we were able to find one of the few left in the country at a dealer in Texas. They are shipping it to us. God willing, total time down at the dealership will be less than 10 days.
I'm actually not salty about the bad water pump; stuff like that happens. But, Stellantis pushing out these trucks without parts to fix them is completely JV. The few pumps left in stock were in the system as unavailable for transfer to another dealer . . . I had to cold call the dealer in Texas myself and make a personal plea to get it. Luckily, the parts manager there was FANTASTIC. If any of you guys are from the Houston area, consider this a personal plug for Autonation in Spring, TX. They really did treat me well when they didn't have to.