You're absolutely right. We usually get dragged down into the mire about NATO this and enclosement that but the fact is, we know there was a campaign of collective punishment on the people of the Donbas starting after the Maidan coup which carried on for almost a decade. The people of the region requested Russian presence to stop the bombing and they did it even knowing sanctions and fighting would come to Russia itself.
People have been begging other countries like Saudi Arabia to intervene in Palestine with something more than rhetoric, this is what it looks like. It's not a fucking Aaron Sorkin show where you do a nice speech and suddenly global politics shift, sometimes force can only be resisted with force. I'm no more a fan of modern Russia than I am of, say, Egypt, but if they chose to give military support to the Palestinian people that would be commendable nonetheless.
Even if that's the case, in what way exactly would this invalidate what the documentary shows? They went to Donbass to get testimonies and images directly from the peoples living here. Are you arguing that all the shelled demolished infrastructure and the artillery fire noises we hear thorough are just a setting and that all the peoples recounting the atrocities they saw and lived through are all paid actors? If so, do you have any evidence whatsoever to prove it? If not, what does Russia's funding change exactly?