'21 RAM Big Horn 3500 DRW CC/LB 4x4 with NEXEN Tire WOES!

So, you found out Nexen tires suck. Not newsworthy although you appear to not have been aware.
And if you somehow can’t find the Michelins in your size (unlikely), then there are plenty of tires just as good and plenty that are arguably better. Just go get some new tires.
Although to your point, I’d think tire/truck warranty may be a possible option? (Idk never had a tire warranty claim, on OE tires.)