If you want the simplest car possible, you can look at models designed to sell in volume worldwide. I'm talking the Hyundai Venue crossover, Hyundai Accent subcompact sedan, Honda Fit/Jazz hatchback (recently discontinued for the US), Ford EcoSport crossover, etc. They are designed to be serviced in poor conditions. They will tolerate removal of electronics like the infotainment because some countries' base models have simpler configurations. In the case of the Honda Fit, the climate control dials physically move the ducts! And repair documentation and parts will be plentiful because there's a large market for parts suppliers to compete. Also look at body-on-frame fleet vehicles like a base Ford Ranger or F-150, but be ready to forgo stuff like cruise control.

There are EV equivalents too, like the Chevy Bolt and Hyundai Kona EV that offer range in the 200s of miles with make driver assists as an optional upgrade. Even with complicated powertrain electronics, EVs are still more reliable than ICE cars because any iffy software is made up for by lack of mechanical parts. The repair procedure is the same as mechnical parts - just swap the faulty part out for a working one, and the "upstream" supplier will probably take the broken module to reflash software or frankenstein together half-working PCBs to make another refurbished module to sell.

If you're worried about remote compromise, it's pretty easy to avoid IMO. Open the dashboard and yank the cellular antenna, and never pair the infotainment to Bluetooth or Wi-Fi (or just yank the 2.4 GHz antenna). Those are basically the only avenues for wireless attacks into a vehicle unless you count the TPMS and key fob radios, which seem too simple and low-bandwidth to offer an attack surface. And if an attacker can access your car's physical ports, they could already attack you in other ways like by weakening the brake lines. Other new electronics, like MOSFETS instead of relays in the BCM, have actually made the car more reliable so they should be fine. Other newly standard features like blind spot monitoring are (1) solid state, so they won't fail often and (2) tolerate failure or complete removal.