You're not alone.
We also purchased a 2021 Lincoln Corsair specifically to tow it behind our RV. We received a notice in the mail last week telling us the car is not towable and providing a white sticker to paste over the Owner's Manual recreational towing page.
Lincoln concierge also submitted our request for a "Good Faith Review", which is more appropriately termed "State Lemon Law Review to Find the Absolute Minimum We Must Do", and we were denied as well. My Lincoln rep was not definitive on when the issue occurred and used phrases like "probably" and "I guess", but he suggested there were cars that had drivetrain issues, these were reviewed by the engineers and determined to be due to towing, and the issue was deemed unfixable.
I am of course concerned because we bought this specifically to tow, and we leave on our next RV adventure in a few days. But also, this car has been towed thousands of miles at highway speeds (new specs state max 3mph for a total of 100 yards) which means that we have been damaging the drivetrain since we've owned it.
We have logged a complaint with our State Attorney General and are looking for a consumer protection lawyer to advise.
Keep making noise. They won't do anything unless they continue to hear from us.