i saw the post where you asked for some resembool characters and infodumping so here u go! :-]
nellie (girl around ed and al's age that they used to play with in resembool)
two farmers who ed talks to (unnamed)
kids they know and help repair things in resembool for (they seem to just be well-known with fixing things around town in general)
teacher and students from their outdoor school (there's more content of her but i can't find it atm, often got in trouble for falling asleep and reading in class. winry did too)
they know the resembool train station guy pretty well! ed talks to him in the manga multiple times too so he still has his job while they're growing up
for traditions they have a thing (at least in the mobile game) where there's a snowy winter festival like christmas but it's called "merry sheep". it's a little ridiculous but make of it what you will haha
there's also a fall festival mentioned in brotherhood for sheep too! lots of sheep related things, ed and trisha seemed to go to it a lot together
there's ANOTHER fall holiday in amestris in general from ssom just referred to as "fall festival" (it might be something more specific though) but it's just a lot of feasting, doesn't seem to be the same as resembool's /w being sheep related or anything haha
hope this helps!!! :^)
I am kissing your hand right now and thanking you for this gift of resources.