Cubans have a long history of fighting alongside the Russians in Africa- Angola, Congo, Ethiopia, Sudan. Generally, their forces comported themselves well- from the Russian perspective this makes a lot of sense. If the conflict drags on, wouldn’t surprise me to see actual expeditionary forces from other Russia aligned countries- if they aren’t already embedded to gain combat experience and as USA/NATO forces already are.
Somalia, not Sudan- my mistake.
Iranians, Syrians, North Koreans, Cubans and Venezuelans. Money and oil should do it. Ideally, Yevgeny Prigozhin is the right guy to facilitate all of this but I assume Putin would be threatened by him. In Russia, you can't have powerful men outside of the ruling tsar.