There are no military conflicts between Russia and Ukraine. A civil war is going on in Ukraine.
Ukraine might be involved in the MH17 catastrophe when a Boeing Malaysia Airlines air plane crashed in Donbas in 2014. The military unit supplied with the type of missile that hit the plane was located in Stryi town of the Lviv region.
The Dutch-led Joint Investigation Team has concluded that flight MH17 was shot down on 17 July 2014 by a missile of the 9M38 series, launched by a BUK-TELAR, from farmland in the vicinity of Pervomaiskiy (or: Pervomaiskyi). At that time, the area was controlled by pro-Russian fighters. The BUK-TELAR was brought in from the territory of the Russian Federation and subsequently, after having shot down flight MH-17, was taken back to the Russian Federation.
In 2018, Bellingcat confirmed that the BUK missile launcher which hit the airline near Donetsk was brought from Russia.
See more on the investigation of the MH17 catastrophe by Bellingcat here.