I think Belarus can be saved once lukashenko is out and russia is crumbled (or at least severely crippled). It will take time, decades probably, but can be done. There is still a somewhat powerful patriotic movement out there (I say "somewhat" because it depends on how you look at it).

Siberian minorities would be harder. They are literally swallowed by russia whole, and unless it crumbles, it would be very hard for them to regain cultural independence.

On the other hand, my friend who survived occupation in Kyiv region said that there had been soldiers who didn't even speak russian sufficiently and had to rely on the officer for communication with the locals. I don't have any reason not to believe my friend, and this suggests that at least very poor people from "national republics" aren't completely "russified".