From Russian article (https://topwar.ru/11444-poteri-sssr-i-germanii-v-vov.html), a kind of scientific study with a lot of sources/tables (including western & German) and all that; TLDR:“human waves” story is bullshit / losses were roughly similar [!] / fighting USSR, Nazis had much more political/industrial and direct military support (and much less “resistance”) from many European countries than western media/historians are telling us. Major part are analyses and “battles” of various sources whose numbers differ dramatically; a couple quotes:

"This article discusses the losses suffered by the Red Army, the Wehrmacht and the troops of the satellite countries of the Third Reich, as well as the civilian population of the USSR and Germany, in the period from 06/22/1941 until the end of hostilities in Europe.

The author does not pretend to seek out the ultimate truth. The data presented in it are available in the scientific literature and the web. It’s just that they are all scattered and scattered across various sources. The author expresses his personal opinion: it is impossible to trust the German and Soviet sources of the war, because their own losses are underestimated by at least 2-3 times, the losses of the enemy are exaggerated by the same 2-3 times. It is all the more strange that German sources, in contrast to Soviet ones, are often recognized as completely “reliable”, although, as the simplest analysis shows, this is not so."

“With all the variety of literature and online resources about the Great Patriotic War, ideas about it in many respects suffer from a certain superficiality. The main reason for this is the ideologization of this or that research or work, and it does not matter what kind of ideology it is - communist or anti-communist. The interpretation of such a grandiose event in the light of any ideology is obviously false. It is especially sad to read lately that the war of 1941-45. was just a clash of two totalitarian regimes, where one, they say, fully corresponded to the other. We will try to look at this war solely from the geopolitical point of view.”

“Much has been written about the exaggerated European “resistance movement” that allegedly inflicted enormous damage on Germany and testified that Europe categorically rejected its unification under German leadership. But, with the exception of Yugoslavia, Albania, Poland and Greece, the extent of the Resistance is myth. Undoubtedly, the regime established by Germany in the occupied countries did not suit the general population. In Germany itself, there was also resistance to the regime, but in neither case was this the resistance of the country and the nation as a whole. For example, in the resistance movement in France, 20 thousand people died in 5 years; over the same 5 years, about 50 thousand Frenchmen - that is, 2.5 times more- died fighting for Nazis.”

"Almost half of European countries - Spain, Italy, Denmark, Norway, Hungary, Romania, Slovakia, Finland, Croatia - joined the war against the USSR together with Germany, sending their armed forces to the Eastern Front (Denmark and Spain without a formal announcement wars). The rest of the European countries did not take part in the hostilities against the USSR, but “worked” for Germany, or rather, for the newly formed European Empire.

A misconception about the events in Europe made us completely forget about many real events of that time. So, for example, the Anglo-American troops under the command of Eisenhower in November 1942 in North Africa fought at first not with the Germans, but with a 200,000-strong French army, despite a quick “victory” (Jean Darlan, due to the clear superiority of the Allied forces, ordered the French troops to surrender), 584 Americans, 597 British and 1,600 French were killed in the fighting. Of course, these are meager losses on the scale of the entire WW2, but they show that the situation was more complicated than is usually thought."

"Franz Halder in his diary on June 30, 1941 recorded Hitler’s words: “European unity as a result of a common war against Russia.” And Hitler quite correctly assessed the situation. In fact, the geopolitical goals of the war against the USSR were carried out not only by the Germans, but by 300 million Europeans, united on various grounds - from forced submission to desired cooperation - but, one way or another, acting together. Only thanks to the reliance on continental Europe, the Germans were able to mobilize 25% of the entire population into the army (for reference: the USSR mobilized 17% of its citizens).

To put it simply, the strength and technical equipment of the army that invaded the USSR was provided by tens of millions of professional workers throughout the Europe."

“Conclusion: The irretrievable losses of the USSR Armed Forces in the Second World War amount to 11.5 - 12.0 million people irrevocably, with actual combat demographic losses of 8.7-9.3 million people. The losses of the Wehrmacht and the Waffen-SS troops on the Eastern Front amount to 8.0-8.9 million people irrevocably, of which 5.2-6.1 million people are purely combat demographics (including those who died in captivity). In addition to the losses of the German Armed Forces themselves on the Eastern Front, it is necessary to add the losses of the satellite countries, and this is 850 thousand (including those who died in captivity) people killed and more than 600 thousand prisoners.”