It was actually fairly equal, with Russians making up around 60% of the SovUnion’s population and 60% of the Red Army.
Ukrainians were around 20% of the SovUnion’s population and 20% of the Red Army, but much of Ukraine was under Nazi occupation - thus, Ukrainians of military age still under Soviet control necessarily were drawn from more heavily or volunteered more readily to get to 20% of the Red Army.
It was actually fairly equal, with Russians making up around 60% of the SovUnion’s population and 60% of the Red Army.
Ukrainians were around 20% of the SovUnion’s population and 20% of the Red Army, but much of Ukraine was under Nazi occupation - thus, Ukrainians of military age still under Soviet control necessarily were drawn from more heavily or volunteered more readily to get to 20% of the Red Army.