This is a question that has been bugging me for a while.
We all know how the "everyone thought the Earth was flat, and that you could fall over the edge" thing is a myth, but whenever someone points out what proves it is a myth, one of the main things I see is references to the calculations of the Ancient Greeks and such, proving that humans knew the Earth was round since very long ago.
But was this not knowledge mainly held by the educated classes?
Whenever I hear these stories, I have a hard time imagining people living in rural areas, and the poor with no access to education having access to this knowledge and treating it like trivial common sense.
Even in the modern day it is hard to get an even basic explanation of how the moon and the tides are related from the average Joe.
I don't think that "all" or "none" is a particularly useful way to phrase it, you can always find exceptions (people today believe in a flat earth, after all).
I answered a fairly similar question a couple of months ago. To quote myself:
by definition if someone leaves behind a written record where they're casually referring to earth as a sphere, they are educated (as in, they know how to write). But we can be pretty sure that a spherical Earth was commonly known from a couple of sources:
the Elucidarium written by Honorius Augustodunensis around 1120 refers to the Earth as a sphere. The Elucidarium was a manual for the instruction of clergy, and was translated into multiple languages. (I'm copy-pasting these from Wiki because I don't feel like retyping them: "Middle English, Old French, Middle High German, Old Russian, Middle Dutch, Old Norse, Icelandic, Spanish, and several Italian dialects.") The lesser clergy were those most likely to preach and minister directly to commoners, of course.
We have surviving sermons from Bertold von Regensburg, a German cleric, that refer to the Earth as spherical (not in the sense that he's revealing a great mystery of the Earth, but as an analogy that his hearers would be familiar with). His sermons were in the vernacular German dialect of his time period (mid-13th century), so there's evidence that he was using that metaphor in the local language that the local people would be aware of.