Russia is in no position to open a second front anywhere. They have shown themselves to be a paper tiger in Ukraine.
The morale of their soldiers is low, their equipment is substandard and in horrible condition, their logistics is a mess, and they have centralized top-down leadership which is ineffective.
They can't build any more tanks because of embargos of critical equipment.
The demographics of the country are a mess.
Putin is cracking down on his own intelligence and military commanders as I write this.
They are a country of 140m people who has an economy the size of Texas, which has 30m people.
Ukraine has managed to grind down their landforces without the significant use of aircraft. NATO would dominate the skies from day 1.
2022 is not 1941.