hi! there's always room for more input on this, but FYI there was a good discussion on this topic a few months ago - see here for the previous responses
Not an expert, nor is it a complete answer, but a perspective on it.
(Eastern) Slavic languages lack articles. In Ukrainian, the prepositions used for at or in are "в" & "на" Also, these aren't direct translations, languages describe things differently, these really are generalities.
Generally when speaking, the preoposition used for conveying location in a city or country is "в" and a region would take "на" somewhat similar to English when we say we live in New Orleans, or in Louisiana, but we use an article when we describe a region such as I'm in the woods, the plains, the countryside, or the South.
I'm not sure, but I belive this also has Russian historical influnce from how it was referenced as part of the Russian Empire because when talking about Ukraine in the context of location, the prepositon "на" is used instead of the usual "в", conveying it as more of a region than a nation. This is usually translated into English with putting an article in front of it.