What do we really know about the Altaic Sprachbund in 2026?

I am aware that Altaic is generally regarded as a Sprachbund, and so on. However, for Sprachbunds we usually have rough estimates of time of formation, geographic location, and the nature of convergence—for example, whether the languages simply converged, converged first and then diverged, or (if they derive from a common proto-language) diverged first and later reconverged.

The only rough estimates of formation time and location currently available assume that these languages share a common ancestor, which contradicts the idea that they form a Sprachbund arising from separate ancestors. This scenario is often linked to the Liao River farming populations, but with the accumulation of more genetic data from Manchuria, it now appears that none of the modern Altaic-speaking populations are meaningfully descended from them.

Since a Sprachbund presupposes large-scale bilingualism, we would expect to observe at least some degree of genetic sharing, regardless of whether linguistic and genetic patterns align perfectly. However, the only shared ancestry we can identify among these populations is associated with Amur River hunter-gatherers. This, in turn, raises another problem: Koreans and Japanese can have up to 20% Amur-related ancestry, yet their paternal haplogroups show less than 1% Amur affiliation. (Again, haplogroups do not necessarily correspond to linguistic affiliation, but this discrepancy is unusually stark—especially when compared to Neolithic European farmers, who were able to retain a much larger proportion of their paternal haplogroups despite substantial Steppe admixture as well as losing their language.)

This leads me to wonder whether Altaic has ever been considered primarily as a maternal-mediated phenomenon like we see in some other language families. Most importantly what is the most updated research on their relationships and how the sprachbund came to be?