It appears that if the Ukrainians have any chance of "winning" (i.e., retaking the Donbas), it would be to cut the Russian resupply arteries. Apparently, the most notable and strategically significant chokepoint the Russians have is the gigantic rail line that runs from Russian onto the Crimean Peninsula known as the Kerch Strait Bridge, which opened in 2018. Russia right now relies almost entirely on railroads for the logistics, especially since we saw what a dog's breakfast their truck fleet was when they tried to advance on Kiev from Belarus, and the Crimean rail line over the Kerch Strait is the most important for their advance into the Donbas.
A website is showing a countdown to the supposed destruction of the strategically vital Kerch Strait Bridge connecting Russia with Crimea. Does Ukraine now have the capability to destroy it?
www.forbes.com
If the Kerch Strait Bridge was destroyed or at least severely damaged to make rail travel impossible (and care was taken to kill railroad workers trying to repair the bridge via drones, etc.), then the Russians cannot quickly bring up new soldiers, fuel, food, equipment and armaments, and light and heavy ammunition to the front. If their big guns do not have enough ammunition on hand to fire upon the Ukrainians or their tanks enough fuel to roll over their lines forward, the Russians are dead because without their prized artillery or tanks, Russia's regular ground forces seem to be about as good as Iraq's were in 1990.
Bottom line: Destroy the Kerch Bridge before Winter, the Russian Army dies in Ukraine. And if the Ukrainians are able to turn around and kill enough Russians in Ukraine, just from a point of sheer demographic decline that Russia is undergoing, the Russians will never be able to threaten a major land war in Europe again for the next two quarters of this century. They just do not have enough young men to send to die to do so. Or even enough healthy
middle-aged men for that matter.