Deploying NATO or UN troops on Ukrainian territory would not be easy. This would depend on the terms of the peace treaty and as far as I know, Russia is against this idea, they would never accept a peace treaty that included this condition. France, England, Germany...want to do it but that doesn't mean they can do it because they don't have the authority to decide that.
The issue of sending European soldiers to Ukraine will be discussed by EU countries directly with Kiev, and not with an eye on Moscow's opinion on this issue. This follows from the statements made by French President Macron during his conversation with the media on Saturday, March 15.
"Ukraine is sovereign. If it asks to deploy allied troops on its territory, whether to accept it or not is none of Russia's business," Macron said.
https://www.ukr.net/ru/news/details/politics/110180268.htmlRussia is currently in a very difficult situation. It is running out of armored vehicles and artillery. The Russian military admits that the Ukrainian Armed Forces have an advantage in drones, which destroy Russian tanks and armored vehicles even before they reach the attack line. Therefore, in some significant areas of the front, the Ukrainian Armed Forces have noted the absence of armored vehicles during assault operations since last year. There are a lot of people in Russia, but they also tend to run out. The irretrievable losses of Russian soldiers on the Ukrainian front have already exceeded 900,000 and this number continues to grow.
At the same time, Putin cannot refuse to continue the war, since the Russian economy has long been rebuilt on a war footing, and a return to a peaceful economy already threatens riots in Russia itself, when the military begins to return home, where the economy and key industries are on the brink of collapse.