Donbas

Russia is definitely getting attrited. Ukraine is too, but not as quickly.

Russia wanted to do two encirclements in Donbas, a very big one which was unable to even launch, at least not so far, and a smaller one, which still hasn't encircled its objective. 

The Russian tactic there may be to try to draw large Ukrainian forces into the forward partial encirclement and THEN launch the much larger encirclement.
IF they have the forces for that: which, spoiler, they likely do not!! Which is shocking but likely true.

The inability of Russia to even effectuate the much smaller encirclement around Severodonetsk is kinda shocking. The only way to explain it as other than a flailing and failing army is that they are trying to lure forces in to the feint smaller encirclement before launching a much larger encirclement. Which is possible! But less than likely given Russians failings at Kyiv and Kharkiv.

The best indirect evidence of the slow motion collapse of the Russian army is their tactic namely:
Take badly trained conscripts into Ukrainian positions, where they will draw Ukrainian fire, likely get slaughtered, and identify the Ukrainians locations
Which are then subjected to MASSIVE bombardments, mostly by artillery
And after a week or so of "softening up" the professional contract soldiers attack to finish off whatever Ukrainian remnants remain.

These are not the tactics used by an army capable of mobile warfare.