The boreal forest is a harsh place for obtaining food and highly favours small and mobile populations like OTL Athabaskan people. Reindeer add a useful dimension but otherwise it's very difficult to settle down. It still would be very interesting to see how a civilisation could emerge in such a forest (or any high-latitude forest like that which covered most of Europe thousands of years ago) given that there's nothing like it among the OTL cradles of civilisation.
I tried something like this as a POD for my TL (I'll refer to it a lot since I dealt with questions like the subarctic being a cradle of civilisation, although with what I know now I would've done it a little differently). Consistent circuits of reindeer herding, shaping the land and selecting plants on those circuits, and permanent gathering centers on the Yukon (it's a similar environment) leading to a more agriculturally focused population. Rich men organise the building of earthworks as ceremonial achievement which just happen to have the uses of flood control and sheltering plants. More edible food = more people and reindeer and the lore gets passed down. There are plenty of edible plants in the Arctic. Lands of Ice and Mice is a great example although in my TL I played it more conservative and didn't have the domesticated forms grow to nearly the sizes needed for true agriculture, instead being supplements to the diet. It helps for them too that the Yukon and much of the American boreal forest has regular salmon runs (I'm not sure which Siberian rivers you'd get a similar regularity) which are an incentive to blend settled and migratory life (even if most people are with their animals wandering around during the year, you still have a core group of people who maintain the settlements, farm, and trade).
I think that given the right incentives (and it could simply be a cultural response to the conditions of nature around them) you'd get something similar at the fringes which could filter down into the wealthier and better off lands (in my TL's case Southeast Alaska and British Columbia's Central Coast, in this case the upper basins of those rivers where many of the major cities are) which might get you a true civilisation based around the rivers and carving out a niche in the forests. I used Sagittaria aquaculture as a staple crop, and there are relatives in Siberia (S. trifolia and S. sagittifolia) which are eaten OTL which might be your basis of agriculture for a developing civilisation. Still, I think even this civilisation would end up eclipsed by others. After all, the North China Plain is a lot more productive for aquaculture of Sagittaria species and has a few other useful crops like millet that would likely get domesticated too and form a secondary region of plant and animal domestication. This would be like my TL where the more productive areas of the Columbia Basin outstrip in wealth and productivity the cultures of Southeast Alaska and the Central Coast.
