I want two clarify two subjects related to Yamna and R1.
In the current stage of our knowledge there is no evidence that the haplogroup R1 formed in Siberia and expanded from there. The oldest R1b we have are from Italy and Ukraine (14.000 and 10.000 ybp respectively ) and the oldest R1a is from Ukraine also. 10.000 ybp.
Siberia is the one of best sampled region and no evidence of any R1 there before the known IE migrations. R1 was present in Central Asia and even Tarim bassein before IE but they were migrants from West.
So the most likely homeland of R1 is the southern parts of Eastern Europe. Black and Caspian sea region. It expanded after LGM, 20.000 ybp, when ices melted. While the oldest R2 are found in Iran.
R1 moved west (V88) east and south before any known IE migration. We can't say when the oldest R1 will be found in Near East. But it was almost certainly present there in Chalcolithic period.
As for the branch R1b-Z2103. It is almost certainly associated with Yamna. But Yamna was very different from any modern population. Calling it European or Caucasian is meaningless.
A straight comparison of it with ancient mainland Europeans (WHG and Euro farmers ) and ancient pops of Armenia show that they were closer to ancient Armenia than any known ancient _unadmixed_ mainland European pop, except the EHG of East Europe offcourse.
Distance to: Yamnaya_RUS_Samara
Distance to: Kura-Araxes_ARM_Kalavan
Distance to: Kura-Araxes_ARM_Talin
European farmers and Yamna are practically equidistant from ancient Armenia.