How is Ukraine a proxy war? It's essentially naked expansionism from Putin. I don't see anyone propping him up.
Now when US funds have stopped we have an excellent natural experiment with which to test your theory. My money is on that the Ukraine war will end soon, as a win for Putin
The Russian advance into Ukraine was stopped well before US arms rolled in. You might want to google 50 mile supply line into Kiev in your spare time.
But you didn't address my point. Korea was a proxy war. Vietnam was a proxy war. Yemen is a proxy war. For it to be a proxy war both sides have to be propped up. So I ask you again - who is propping up Putin?