I bought a 2018 3.5 ecoboost brand new in late 2018. I towed 7,000 pound trailer over 15,000 miles with it. Plenty of power, good mpg when not towing, not good mpg when towing. I wrote up a lengthy review of a 5,000 mile trip towing to California and back on here if you want to search it.
I bought it fully aware of timing chain stretch that can affect "some" of the 3.5 motors. With over 800,000 F150's sold a year and majority of them Ecoboost of one or another configuration, I took those odds.
Well, in 2021 with 53,000 miles on the timing chain stretch got so bad that the truck was in the dealership for about 2.5 months waiting for techs to fix it right. 3 attempts didn't fix it. The ford dealership was such aholes about it, I dumped it and purchased another truck from a different brand.
Its a shame really, I had two excursions, a couple of F series trucks, and because of that ONE truck and the way Ford and the dealership(s) treated me I am out.
I buy a new truck every three to four years, and I know I won't be getting another ford anytime in future.