First, it isn’t just all of the 30 NATO nations aiding Ukraine, in total about 54 countries are.
Here are two examples of Russia aiding countries, one was a United Nations war and one was Vietnam, in both cases Russia was also supplying troops.
Korean United Nations war.
“Despites its denials at the time, the Soviet Union was intimately involved in the Korean War. The contribution made by the Soviets was vital. They provided diplomatic support, strategic and grand tactical planning, including the planning of the invasion of South Korea, and essential logistical support. They supplied and trained the air forces of China and North Korea. Soviet pilots flew aircraft with Chinese or North Korean markings and after the war claimed to have shot down over 400 UN aircraft.”
Thousands of Russian served in Vietnam
“Starting in 1964, North Vietnamese fighter pilots and anti-aircraft gunners were being trained in the Soviet Union, with Soviet advisors also being stationed in North Vietnam. Early on, when the North Vietnamese troops were still unfamiliar with the new Soviet anti-aircraft batteries, Soviet crews manned the guns themselves and these crews did, in fact, shoot down US planes. One such Soviet battery reportedly downed six US planes.”
“Soviet involvement was not confined to anti-aircraft crews. There were also widespread reports (though these were never confirmed) that Soviet snipers had embedded with NVA units and infiltrated South Vietnam to test their new SVD Dragunov sniper rifles. Witnesses described these snipers as white men with blue eyes.
Beyond South Vietnam proper, but still within the unofficial theater of the war, Soviet GRU Spetsnaz special forces took part in at least one, and likely more, ground combat operation. In 1968, a team of ten Spetsnaz attacked a covert US base on the Cambodian-Vietnamese border, destroying three of the then-new US Cobra attack helicopters and actually stealing another. This operation was confirmed only after the fall of the Soviet Union, and if there was one Soviet special forces mission, there were almost certainly more.”
“From 1968 on, the Soviet Union provided the vast majority of the military and economic aid that North Vietnam received. They supplied their communist allies with food, petroleum, transport vehicles, iron, steel, fertilizer, arms, and ammunition. Most critically, the Soviets supplied all of this as aid rather than loans (as the Chinese had done early in the war). This eased the economic strain on North Vietnam and further advanced their war effort.”