I agree with BGcoop. Feather/wing sexing is possible, but only on crosses of chickens with certain genetics (not the majority of chickens). Also, I've only seen reliable articles (with scientific explanation) do it on day-old chicks, not older birds. It would look like this, where the primaries in the female are longer than the coverts, while the male has primaries and coverts of the same length.
Here's a good article explaining the genetics behind it.
https://www.amerpoultryassn.com/2022/06/feather-sexing-in-poultry/
Again not something that happens in the majority of chickens, so isn't really reliable unless you're breeding a specific cross.
I know it's common to see little diagrams with chicks starting to feather already (like this one):
But I just haven't seen any good scientific evidence for that yet! It's always the little farm blogs reposting it. Wouldn't hurt to try it on yours though and see if it's accurate!
Personally, I would wait until they are 5-6 weeks old and look at the face. Comb and wattles on males will be bigger and brighter than on females. That is how we sex them here. You might be able to see differences as early as 3 weeks. By 8-12 weeks (as BGCoop is recommending), you'll start to see pointy hackle and saddle feathers coming in for males, and it will be pretty obvious by then.
