For those who read Russian, here's an interesting set of interviews - from a Russian dissident publication - with three Russian convicts who had been recruited into the Wagner mercenary army based on promises of pay and commutation of their sentences.
I don't have time to translate. But, basically, they recount severe mistreatment and being thrown into the meat grinder of combat with little equipment and training. The three men surrendered to the Ukrainians, and were interviewed after being captured (probably in or around Soledar, where there is currently heavy fighting). They also describe the different gradations of convicts in the Wagner forces. "Cocks" (men who were sexually abused in prison) are the lowest of the low, and get put in a special unit. Ditto for rapists and child molesters. Regular violent criminals and thieves (like these three men) are treated better. Finally, "Rexes" - drug users, most of them in for drug offenses - have the highest relative status, and get used as "storm troopers" (though this also involves even greater risk).
The regular Russian military is also notorious for poor treatment of troops - especially recently drafted mobilized men ("mobiks"). But this seems worse.