On dissolution of the USSR in 1991, Ukraine and the Russian Federation became independent sovereign countries, and there was no conflict between them.
In 2014 a nationalist Ukrainian group, encouraged and assisted by "the West" (state and non-state actors), took over the government of Ukraine, which has lead to Crimea voting by referendum to leave Ukraine and join the Russian Federation. This is not surprising, given that Crimea was under Russian sovereignty for over 200 years and in 2014 had 65% Russian population, while 23 years under Ukrainian sovereignty with 15% Ukrainian population.
Also the majority ethnic Russian population areas of Donetsk and Lugansk proclaimed independence from Ukraine.
Unwillingness of the nationalist Ukrainian government to acknowledge the independence of these "breakaway" republics has resulted in a civil war, with the Russian Federation seeking to protect the Russian population of these republics and a ceasefire agreement (Minsk Protocol) was reached in Minsk in 2015 between Ukraine, the Russian Federation and OSCE.
This agreement, however, did not stop the hostilities between the Ukrainian government and the two republics.
Earlier this year some Ukrainian politicians used the slogan "Crimea is Ukraine!", which was echoed by US/EU/NATO Media and politicians, which has inspired the Russian Federation to hold military exercises on their own territory near the Ukraine borders.
These exercises were followed by the present US/EU/NATO campaign of accusing the Russian Federation of "aggression" and predictions of imminent Russian invasion, which the Russian Federation government denies. The Russian Federation, however, also set out demands to the US/EU/NATO to keep out of Ukraine.
From the above it follows that the cause of the conflict between Ukraine and the Russian Federation is the status of Crimea, Donetsk and Lugansk.
To end the conflict between Ukraine and the Russian Federation permanently the following steps need to be taken:
The implementation of the above conditions will end the present conflict between Ukraine and the Russian Federation.
To end the US/EU/NATO Cold War against the Russian Federation, the constituent members of NATO need to disband this military alliance, because it was created at the time of the Cold War between the USA and the USSR, and, after the dissolution of the USSR in 1991, NATO has lost reasons for its existence.
Continued existence of NATO and of the Cold War thinking, that still remains in the USA and Europe, are perpetuating hostile relations between "the West" and the Russian Federation.
Dissolution of NATO will bring peace and stability to Europe.