“Considering nearly every agreement between Russia, the EU and the USA has been broken any agreement to end the war would have to have some pretty concrete guarantees between the warring parties.”
Looking at human history, there are no long term “concrete guarantees” between nations. Alliances shift, treaties are broken or sunsetted. Nations that survive act in their own self interest. When interests change, treaties and allies are abandoned and new alliances are formed.
The present government of the United States has turned on its own citizens. The US government has a history of abandoning agreements including the many atrocities associated with broken treaties signed with Native American tribes. In recent decades the US government has invaded multiple countries or topple regimes through covert activity in the name of installing democracy around the world. Yet at the same time it spies on its citizens, censors free speech, and fails to protect the homeland from invasion. Why would any nation today believe a treaty or alliance with the United States would be “concrete”.
That’s all true, which makes it difficult to see how an agreement between Ukraine and Russia would get negotiated.