Surprised she didn't pull the "invent the microscope to prove bacteria" isekai angle here. Their civilization already has lenses (some people have glasses), so getting someone to make one shouldn't be too outlandish.
And the web and light novels for this title are completed too. At worst the manga is just a promo for the novels (u want to know how it ends, go buy the novels!)
It should be the Poles or Lithuanians though, since vodka was invented in Poland and achieved its modern form in the Polish-Lithuanian Commonwealth (Russians, Swedes, or Norse would work too, since they're all major producers of the stuff). Additionally, no Balkan state is considered part of the "vodka belt."
Or they were referring to "Balkan 176°" — a specific modern vodka made by a Bulgarian company with an unusually high ABV. Thing is, as far as vodkas go, it's not widely known. The author messed up again: it's not high starch content but high sugar content. In fact, the reason why starchy plants can be used in alcohol production is that starch is essentially a complex sugar. For the same reason milk, especially cow's or ewe's milk, can be used to make alcohol: milk contains lactose, another complex sugar (that "-ose" ending is a give-away). On the flip side, too much sugar and no fermentation (or spoilage) occurs — to make mead you basically just dilute honey with water and then ferment it like white wine or cider.