Update:
Tow truck arrived and we used his booster pack to jump start the truck. It worked. My truck took an extra second and then started up. He disconnected the booster pack and my truck seemed totally fine.
So, the tow truck driver left and I went to drive it for a bit to let the batteries charge back up. The Voltmeter on my dash said the battery was at 14V. Cool.
I left my house and immediately got on the Interstate (onramp 1/2 a mile from my place), thinking some steady driving at a higher speed would be the best way to charge the batteries.
My Voltmeter was still showing 14V. After a couple of miles on the Interstate, it was showing something like 13.1 V.
Shortly thereafter, a TON of warning lights all illuminated on my instrument cluster. I was approaching the next exit down from my house, so I got off there.
The engine was still running.
When I stepped on the brakes to slow down for the offramp, I discovered that I had almost no brakes. All power boost function was gone. The only braking I had was whatever manual hydraulic force I was generating by mashing the brake pedal hard. But, that did slow me down. I did not rear end anyone. Thankfully, I was driving much more conservatively than I normally do.
At the end of the offramp, I was able to go right without stopping, so I did.
Then I came to a stop light and had to stop. The engine was still running. I was the 2nd car in line at an intersection where the road I was on was 6 or 7 lanes wide. The cross street was a 4-lane. It was 5:00 rush hour traffic.
I thought "maybe if I shift it into Park and then back to D that will reset something with the brakes."
Be smart. Do not be like me. As soon as I shifted into Park, I felt some kind of motor in the shift knob assisting the last little bit from R into P. Once it was in P it would not let me turn the knob back out of P.
So, now I am sitting at a light in the middle lane of rush hour traffic and I cannot move. FUUUDDGEE! Only I didn't say fudge.
I thought "well, it can't get any worse. Let's see if I can turn it off and then start it again."
Nope. I mean, I was able to turn it off, but there was no starting it again. I think the dash Voltmeter was now showing 6 or 7V.
So, I turned on my hazard lights and called 911. They said help was on the way and hung up. Then I called Stellantis again to arrange for another tow truck.
While I was on the phone with Stellantis, my truck battery fully died and my hazard lights shut off.
I was a sitting duck.
At that point, I prepared to abandon ship. I was just waiting for the light to turn red so the traffic around me stopped and I was going to get out and go stand on the corner. That was when the cops finally showed up.
So, eventually I got it towed to the dealer, dropped off after hours of course. Now I just have to wait until tomorrow to see what's going to happen.
Fudge.
I'm guessing it must have a dead alternator. Assuming so, any thoughts on whether the batteries will be okay if they just replace the alternator and charge the batteries? I feel like being at 5V (main) and 2V (backup) earlier would indicate that they have discharged too far and need to be replaced.