My daughter needed a 21" front in Egypt, so we asked in various tyre shops in Cairo. In one, the owner's son rode a bike and we found a tyre on the road where most of the bike shops are.
Made in Taiwan but with maker's name proudly displayed on all the wrapping (so it wasn't a fake Pirelli or something), and it looked OK. About 15 GBPounds.
Now in Khartoum and it still looks good.
But we went into the Western Desert after Cairo.
There are thousands of bikes ridden by the oasis-village locals all over the desert. They don't use knobblies, just road tyres and they do a lot better than us!
In Farafra there are lots of bike shops, each one having a good display of new tyres, including knobblies, hanging from the ceilings.
In Cairo we only found the one knobbly. In Farafra there was a choice.
So I came to the conclusion if you want to ride on the local African roads, buy the tyres that all the locals use!
PS. I took a spare rear tyre with me. Strapped on the back horizontally, it actually provides a neat extra luggage rack, sort of upper deck, so you can strap even more stuff on top!
It's fitted now, and the discipline of now having to ditch the luggage that was strapped to it is definitely a good thing.