You believe they are not allowed to leave Ukraine

well maybe during the war. Really there has never been much of a desire from anyone to do that. I had time to look into in it 2014 time and really most of all their was a country called Russia trying to get them to think that way. So apart from parts of the Donbass and the other place beginning with L, I would say there is no place with anything near a majority of Russians wanting to leave. How many want to leave even in those areas is questionable. What I have heard is Russian after Russian after Russian as their home and that of their friends are destroyed telling Putin they very much do not want this. So now we look at whether you can take a bit of the Donbass and the L region. Generally speaking countries need to go through proper protocol about leaving. I am not convinced there is a majority in those regions who want to. Sure you can take them back to Russia and leave the land clear if you and they want,