Russia has never interfered in the internal affairs of any country. Neither the EU countries, nor any other country in the world and do not want to interfere. This is our most important difference to the USA and its allies, who, for example, supported the overthrow in Ukraine in February 2014.
Since 1991 Russia was involved in several international conflicts, including intervention in neighbouring states, such as Georgia in 2008 and Ukraine in 2014.
It was also Russia that interfered in Ukraine. In 2014 Russia annexed a part of Ukrainian territory - the Crimean peninsula. The so-called referendum on the peninsula was organised in a matter of weeks by a self-proclaimed Crimean leadership lacking democratic legitimacy and installed by armed Russian military personnel following the seizure of public buildings. No international body recognises the so-called referendum, announced on the 27th of February 2014, and held on 16th of March 2014. For the EU statement on the fifth anniversary of the illegal annexation of Crimea see here. The United Nations General Assembly Resolution No. 68/262, adopted on 27 March 2014 and supported by 100 states, clearly says that Russia's actions in Crimea as well as the referendum held in the Autonomous Republic of Crimea violate international law.
Russian President Vladimir Putin admitted military presence of Russia in Ukraine in 2015.
Moreover, numerous investigations have provided convincing evidence of Russian interference in the Brexit referendum and in elections across Europe and in the US - see more information here, here and here.