Crimea became part of Russia, once again, after the March 2014 referendum, with 96,77 percent of the Crimean electorate and 95.6 percent of Sevastopol’s population voting in favour of joining Russia. This came after the toppling of the regime in Ukraine, in February 2014.
Summary
Russia is not going to threaten the sovereignty and territorial integrity of the former territories of the Soviet Union. No one can exclude the possibility that Ukraine will start disintegrating itself, as the regional elites no longer need Kyiv. Poles, Hungarians, and Romanians have their eye on the Ukrainian territories, which historically were part of Poland, Hungary, and Romania. As the situation deteriorates in Ukraine, protection of national minorities will become in issue. Furthermore Nazi structures, prominent in Ukraine, may push the government to attack Donbas.
Disproof
Conspiracy theory perpetuating several recurring pro-Kremlin disinformation narratives about disintegration of Ukraine, war in East Ukraine, as well as Nazism and Russophobia. Russia is, in fact, violating territorial integrity and sovereignty of Ukraine with continuous acts of aggression by the Russian armed forces, ongoing since February 2014. Poland, Hungary, and Romania adhere to international law regarding state borders and have no territorial claims upon Ukraine.
See earlier disinformation cases alleging that Neo-Nazis have an outsized influence in Ukrainian politics, that Poles are stoking nationalist sentiment in Ukraine in order to annex Lviv, that Kharkiv, Odesa, Mykolaiv, Zaporizhzhia are willing to be part of Russia, and that real Ukrainian patriots fought for DPR/LPR.