AFAIK Air Serbia is still flying to Russia, and even doubled number of flights few days ago because of demand. I don’t know what’s the situation with visas, how long you can stay, how it is to open bank account, etc but historically Serbia is friendly towards Russia. Government does condemn Russia for this war, but I don’t think we’ll be implementing any kind of sanctions. Elections are in a month, and noone wants to loose votes of pro-russian part of population.