The fact that 1 in 3 Americans aged between 18 and 24 believe the Earth is flat (Unimelb article)

Going to the original article linked there
(here): Of the 34% that don't reply "I have always believed the world is round", nearly half (16%) say "Other / Not sure" (hard to know what that means - but notably there is no category for "I used to be unsure or believe the world is flat, and now I believe it's round"). 9% are saying they are now skeptical of the earth being round, but 5% are saying they are now skeptical of the earth being flat. Hard to count both of those simultaneously as flat earth believers. Only 4% overall say they have always believed the earth is flat. Trying to get at people's
current beliefs by asking them the history of their beliefs seems like a bad idea.
So yes, the numbers are higher than in older age groups, which is a concern - but I'm not sure it's as bad as 1/3 sounds.