Fight the tyrant, not the Russian army. I believe the sort of thing that the OP is asking for, if we restrict ourselves to just Russia for the moment, is: is there any way to assist with getting rid of Putin, reducing the harm he causes, or preventing the next Putin after he's gone? Focusing in further on the first of those: Is it helpful to donate to democracy-enhancing initiatives in Russia? (Is it possible to help get Putin voted out? The answer is apparently no.) Can one help to get him overthrown? It seems possible, if he were to become unpopular enough. Is supporting independent media in Russia possible and helpful? There are plenty of rich oligarchs Putin has wronged, so a priori expect that more money is probably not going to help. Clever initiatives to help people see past state propaganda and get around censorship could.

The harms created by Putin are vast and the hopes to do anything about them are minuscule. This makes it exceedingly difficult to estimate what the expected value of any intervention is.