I have to say "Eastern European" is a quite poor and unhelpful generalization nowadays. It is ethnically and linguistically diverse: Slavic, Baltic, Finno-Ugric, Romance (Romania) as well as Albanian and Hellenic. It is religiously diverse: Catholic, Protestant, Orthodox, Muslim and even the bastions of irreligion/atheism (Czechia and Estonia). There are significant cultural differences, especially comparing the more…
I think the right solution here is to divide the region into Central Europe, The Balkan Region, and The Western CIS and Caucasus:
https://www.researchgate.net/figure/The-Map-of-Eastern-Europ...