VsKO.

This is coolbert:

I had thought there was probably something to this and I was right! 

Yet one more distinct ethnic group their participation in the Ukraine Conflict. 
Chechen, Buryat, Komi we already know of. And as has been during the case with the stalemated war commencing in 2014 the Cossacks. [please note dates both # 1 and # 2]

1. "The Role of Cossacks in the Re-Invasion of Ukraine"

From https://newsaboutturkey.com | 2 Mar 2022.

"In Russia’s aggressive and unprovoked war against Ukraine, much of the global attention has understandably focused on the actions of the regular Armed Forces; but the Russian Cossacks are also playing a role in the conflict. On the opening day of the re-invasion, the head (ataman) of the All-Russian Cossack Society (Russian acronym VsKO), Nikolai Doluda, published an article reminding that “in 2014 the Kuban Cossacks were the first to come to the aid of the inhabitants of Crimea and held the onslaught of the Banderites [sic] on Chongar, Perekop, and Turkish Val; so today, the Cossacks of Russia do not stand idly by, but are aiding the residents of Donbass"

2. "Moscow creates new ‘Cossack’ paramilitary units for possible use against Ukraine"

Article by: Paul Goble | 2020/04/11 - original story "The Jamestown Foundation Publication".

"Recent reports that Moscow is deploying Cossack groups along the Russian-Ukrainian border near the Kharkov, Sumy and Chernihiv regions of Ukraine are extremely worrisome, as the Kremlin ostensibly used similar units in its initial invasion of southeastern Ukraine in 2014. Such revelations may presage a new Russian move against Ukraine and be intended as an attempt to muddy the waters about who is behind any aggression"

Cossacks their society organized along strictly military lines. Cossacks as a people enamored of war and greatly fond of the old ways. To war by horse if possible. 

coolbert.