This narrative claims the war in Ukraine is a civil war and Russia has nothing to do with it, consistent with common pro-Kremlin disinformation about the war in Ukraine.
OSCE representatives have stated about the presence of the Russian military in Donbas and personal communication with them. For example, a representative of the Organisation for Security and Cooperation in Europe in Ukraine Alexander Hug said in an interview with Foreign Policy in October 2018 that the OSCE mission had identified people with Russian insignia in Donbas, as well as prisoners who claimed to be servicemen of Russian Armed Forces.
There is extensive evidence of active Russian soldiers taking part in fighting in Donbas. Most of the Russians captured have already been exchanged. Amid heavy battles in 2014 and 2015, the Ukrainian army captured dozens of active Russian servicemen in Donbas. For instance, on 24 August 2014, amid the Battle of Ilovaisk, the 51st brigade captured 10 Russian paratroopers from the 331st parachute infantry regiment of the 98th Guards Airborne regiment based in Russian city Kostroma. Later, Russia claimed that the soldiers simply got lost on Ukrainian territory. On 31 August Ukraine and Russia exchanged captured troops.
On 15 May 2015, the Ukrainian army captured two Russian GRU soldiers – Capt. Yevgeniy Yerofeev and Sgt. Aleksandr Aleksandrov. A year later they were exchanged for First Lieutenant Nadiya Savchenko who had been captured near Luhansk in June 2014 and then transported to Russia.