The buffalo bike is one that was specifically made for developing nations and the project prioritizes local assembly and repair, while the bike is designed to sacrifice weight and aerodynamics, instead offering heavier-duty parts like thicker rims, puncture-proof tires, high-capacity racks, etc. This bike has two chains to reduce the likelihood of a critical failure and an internal coaster brake hub which is more robust to the elements.
Your average low-cost bike isn't intended to be used in environments with rough terrain and high contaminant concentrations without regular maintenance, and especially older bikes with things like cup and cone bearings which are more susceptible to dirt getting in, thinner tires which puncture more easily, and nonstandard bits and pieces like derailleur hangers which predate the UDH standard.
The best bikes I saw were ones that a kid from a family could buy for maybe $20 in local currency and the repairability comes from the cheap cost - if something breaks down, you can find the replacement part from a spare bike that broke down months ago.
I'm thinking that in the west we either have very cheap bikes that aren't really designed for long term use, and more expensive bikes tend to use fancier parts.
Off the top of my head. Steel frame, can be repaired / modified with any old welder. Designed so it can be taken apart with the minimum of generic tools. Standard bearings, brake blocks etc (probably brake blocks that you can shove some piece of old tyre in).
Front forks and the crank require special tools to remove. I assume the free wheel assembly would be the same. I don't know if it would be possible to modify these to be serviceable with basic tools, the point is an African could probably work out how to fix a bike, the issue would be affording tools and spares, and availability of those tools and spares.
So basically just your average cheap crappy Halfords Bike-Shaped Object type "bike"?
"very cheap bikes that aren't really designed for long term use"
You want cheap and reliable, not cheap with a load of doodads to make it seem expensive.
You still have the problem that the bits that you cannot just knock up out of old Morris Minor steering columns or AK47 barrels are the bits that break.
I know one person who has legitimately worn out a bike frame, in 40-something years of cycling, and it wasn't me. It was a guy who rode his bike about 50 miles *every single day* and rode from Edinburgh to Glasgow and back a couple of times a week. Eventually it started cracking around the welds.