Can someone unequivocally clarify if this sentence implies that the person is not living in Siberia anymore? My guess is 'I have lived in Siberia for a long time' (and still live there) would be something like 'я давно живу в сибири'? I know it's been asked before but there are barely any upvotes to those comments, so I want to make sure.
Since Сибирь refers to a geographical area with no actual legal authority as a whole, since it consists of many области, I would expect the preposition на to be used here, much like one used to на Украине before the independence of 1991.
Can anyone explain why the preposition в is used?
The preposition that needs to be explained here is not в but rather на as used with Украина. It’s not because Ukraine was a "geographical area with no actual legal authority" (it wasn’t since 1918 at least, and it doesn’t matter anyway) but probably because the word is akin to окра́ина ("outskirts", "borderland"), which is used with на. And на Украине is still used (mostly) in Russia, while в Украине is used (mostly) in Ukraine, in both Russian and Ukrainian (and, I believe, was used long before 1991) — see Name of Ukraine.
Sorry, forgot the prepositional -е ending. I ment ‘на Вкраїне’.
In Ukrainian itself, there is a "euphony rule" sometimes used in poetry and music which changes the letter У (U) to В (V) at the beginning of a word when the preceding word ends with a vowel or a diphthong. When applied to the word Україна, this can produce the form Вкраїна (Vkrajina), as in song lyric Най Вкраїна вся радіє (Let all Ukraine rejoice!).
Well, there is no such rule in Russian.
Unrelated, but "in Ukraine" would be на Вкраїні. (In old Russian orthography, the prepositional and dative ending -е was spelled -ѣ; knowing that, one can safely assume that in Ukrainian it’s -i because the old yat (ѣ) sound in Ukrainian changed to i, and in Russian to e.)