They were the cannon fodder of the Russians before the advent of the Wagner’s convivts and the Storm Z units. They had very considerable losses and today just a small part of the soldiers are from the Donetsk and Luhansk Oblasts, the vast majority now being mobiks from Russia proper.
The units were reformed and became brigades or regiments of the 1st Corps (DPR) and 2nd Corps (LPR), both part of the 8th Army of the Southern Military District (under whose operational control they had been since as early as 2014). They received new equipment (e.g. T-80BVs and BMP-1/2s) and are mainly used for defensive purposes to hold the lines from the Siversky Donets to Marinka. Sometimes they are used for offensive purposes (Bilohorivka/Spirne, Avdiivka/Pervomaiske), other times they are sent elsewhere under other formations that need reinforcements (as is happening in the Southern front). Today they are regular motorized infantry, albeit the lowest quality one in the Russian Army.
Certain battalions perceived as “elite” in the structure of the separatist corps and with a history starting in 2014 (Sparta, Somalia, Vostok, Pyatnashka), on the other hand, are mainly manned by Russian volunteers.