I remember reading somewhere that the indigenous people of a SE Asian country believed that orangutans could speak, but chose not to because they would be forced to work if humans found out

There’s some really amazing world building that’s been done with flat-earth art as a springboard

Can’t remember the name, but there’s one with concentric circles separated by ice walls with landmasses named after different mythologies’ deities. There’s a whole community built around writing lore for each landmass