In an attempt to not misinform others coming to the site, this is correct for typical 2WD vehicles, but does not apply to most 4WD vehicles. The Ram 1500 4WD is absolutely capable of being flat towed as long as the transfer case is placed into Neutral just as
@SportyJames said. This effectively disconnects the transmission at the transfer case and you are free to tow it with all 4 wheels on the ground. Also, you do not want to just simply disconnect the rear driveshaft because without the driveshaft, fluid will leak from the open connection on the transfer case causing damage.
Reference:
2021 RAM 1500 Owners Manual PG 230
Now, I just wish I was cool enough to have an RV worthy of flat towing a TRX behind it to the dunes
... because this beast is definitely not fitting in the garage of my toyhauler!