Hey there, playing the Beta 8026, and I noticed something quite different from the current official V43 : the AI does not like to settle new cities. But maybe it has something to do with the options I used in this game.
I use the combination of "City starts with one tile" and "Realistic culture spread" so maybe the AI does not see the point of building a city with only one tile in the beginning.
Or it comes from the "Happiness penalty" which penalizes overexpansion, but I remember a game in V43 where one AI did not hesitate to have 24 unhappiness penalty from overexpansion.
Another option that might be problematic would be "Strict vicinity", making new cities less interesting, I don't know.
I included my save, I play in immortal, we are reaching the end of prehistory, I have 5 cities and a majority of the AI opponents only have their first city, a few have 2, but it's rare.
It's true that the settler units can be very expensive, but here clearly the AI does not like to build them