Ukraine

300k+ out of Russia’s total population is like one in 500, a small city/village of 10.000 would have like 20 soldiers that just doesn’t show any signs of life any more.

Don't forget about the 800,000 to 900,000 russians that fled the country since the start of the war to avoid being meat for the grinder. source

The other thing that will make the dead and escaped more noticeable would be the gender and age concentration. All of those disappearing will likely be men between 18 and 35. Russians are going to start looking around in public and seeing vastly higher numbers of old men, children, and women.

Lastly, there isn't an even distribution of where these men came from. It might not even be noticeable in Moscow, but in Buryatia all the men may be gone.