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.
As I said before, it would be very difficult for Europe to send troops to Ukraine without the consent and support of the United States.
Just days after making a bold announcement they would send troops to Ukraine. On March 26, Europe withdrew the plan and said that the idea was no longer attractive with the current situation.
Like Ukraine, Europe seems to have no voice, influence or ability to make any decisions on its own in this war, but it is deliberately trying to show that it has great influence.
https://nypost.com/2025/03/26/world-news/europe-walks-back-plan-to-send-troops-to-ukraine-over-logistical-hurdles-lack-of-us-support-not-very-sexy/Even their closest allies scoff at what Europe is proposing and doing.

https://www.reuters.com/world/europe/europes-talks-ukraine-security-shift-sending-troops-2025-03-26/