Russian Socialist Movement (emigration branch):
"In contrast, the defeat of Putinism in Ukraine would likely lend momentum to movements for democratic change in Belarus, Kazakhstan, and other former Soviet countries, as well as in Russia itself.
It would be overly optimistic to claim that defeat in war automatically leads to revolution. But Russian history is replete with examples of military setbacks abroad that have led to major change at home—including the abolition of serfdom, the revolutions of 1905 and 1917, and Perestroika in the 1980s."
https://fourth.international/en/europe/504
(PS. I've never even been close to the Trotskyist tradition, but compared to all other kinds of self-professed Marxist parties in the world, I must say that the 4th International stands out by holding a clear line in solidarity with Ukraine and in condemning Russian imperialism.)