Many data points indicate Ukraine is running out of men, including very old and very young on front line. Harsh forced conscription of men off the streets (like old style British Navy press gangs), very large population loss since start of war, very low fertility and bad demographics long before the war etc.

This is an interesting analysis

Anyone claiming Ukraine has the world's largest reserves is utterly deluded and mathematically challenged. How can a country of 30 million have more reserves than India or China with well over 1 Billion.