There is a core “Russian” ethnicity made up of some Slavic, Finno Ugric, and a little Mongolian Ancestry, located around Moscow.
However east Asians in Kamchatka are also “Russian”, as are the Turkik peoples of Central Asia, as are the Chechens and other Muslim populations of the Caucuses.
So what is “Russian”?
An ex- mid-level Soviet bureaucrat once told me they used to joke that if you beat a Polish man long enough, he becomes “Russian”.
“Russian”, once you get away from the core group who regard themselves as “greater Russians”, is not an ethnicity but a shared historic trauma.
For example: the annihilation of Grozny turned Chechens into “Russians”.
Russian identity is fragile, largely because they’ve expanded, conquered, and oppressed in all directions, and are reviled by their neighbors.
To prop up their identity they rely heavily on victory over the Nazis in WWII. Hence, their domestic propaganda insists that the invasion of Ukraine is a war on Nazis. Earlier, I accumulated articles showing Russians separately calling every single one of their European neighbors, from Finland to Georgia, either Nazi or fascist. Sadly, I didn’t make backup copies and most of the links are no longer live.
Interestingly, the years 1939-1941 do not exist in Russian history. Their over collaboration, and material and political support of Hitler would be a devastating blow to the foundation of their identity. As far as Kremlin propaganda is concerned, WWII began in 1941, and there were no invasions of Poland or Finland.