Defensionem has a Facebook post on Nukes. I found this interesting though:
Ultimately, as stated multiple times, to the dismay of a few social media fanatics and fundamentalists, this will likely lead to a longer conflict that further ruins the internal functionality of the Ukrainian state and places them in the same category as Haiti; a bankrupted, broken, internally gutted and fully in debt nation without an economy, and post conflict, fully reliant on foreign aid to exisit, regardless of a Russian defeat or withdrawl.
*Additionally, as this author has stated numerous times, the above situation for Ukraine, is the truewithdrawal and goal of Russia.*
So they believe Russia may well be satisfied with a bankrupt and failed Ukraine. They also don't think nukes are likely unless the Russian army is thoroughly routed. As in, surrounded and in danger of mass surrender. Or if Russia believes that some combination of Ukraine/NATO will cross the border into Russia. As long as the Russian army can retreat toward Russia, and Russia feels their border is safe, the author doesn't believe Russia will resort to nuclear weapons.
So in other words, they view it as unlikely. But they suggest if it happens it has been thoroughly wargamed. If the west retaliates against Russia, Russia has a lot of options. First, and easiest, destroy Berlin or Paris (or other cities in range). This can be done conventionally. Second, attack or nuke Sweden or Finland. Neither is part of Article 5 yet. And of course, attack a US target.
The prospect of nuclear weapon use by Russia is real, but under specific conditions. The goal is to not allow that possibility to materialize. If it does and were Russia to in fact employ them, however limited, there would not be any winners and the response options would likely lead to further destruction and loss of life.