A few million miles in semis with 18speeds, never a problem.
Several Jeeps and Fords with clutches, never a transmission issue altho a few got rebuilt engines.
Fewer than 10 vehicles with automatics and 3 of them cratered. 2, on the highway a thousand miles from home.
My wife only drives automatics but she never ventures far from home and she has never owned a vehicle more than 5 years old.
Overlanding in a foreign country, with a choice, I'd never pick an automatic. Shifting gears "might get old" .... lol, never for me. I like picking the gear I want.
I've never needed to replace a clutch. 400K kms on my TJR, second engine, original clutch. 200K kms a year on a variety of semis with 18 speeds, never "needed" a clutch on the road. There are several advantages to a clutch like bump starting. Parking on a steep slope in 4LO in gear with the engine shut off beats the heck out of trusting "park".... or the parking brake.
And then there is the expense of rebuilding that automatic. When my 5.9 Grand cratered 1000kms from home, it cast $3500 to get it fixed..... in Calgary, a major center in Canada. No idea what that might cost in South America. And when an automatic craters.... I'm not sure you get very much warning. It just goes. I have never been stranded with a manual even when Ford forgot to put oil in the tranny during the 12,000 mile checkup. 1000 miles later without oil, it locked in gear, thankfully second gear, and we drove 100 miles on forestry roads to High Level.
Automatics when they die they stop. Manuals when they die they often keep moving.
Off roading.... if I know the transmission is well maintained regardless, manual or automatic, the automatic will rule. As long as service is readily available an automatic is mindless, effortless, fabulous off road, especially in 4LO. To do as well in a manual, you need for more skill, you really need to pay attention with a clutch. But weighing the odds...... on an expedition to a foreign country.... I'd only consider a manual tranny.
I'm thinking mechanics in third world countries are pretty adept at keeping manual trannies going no matter how remote you are. Not sure you will find the same skills for a modern computer controlled automatic.