I think the idea of R1b's ancientness has been revisited several times by academia and every single time successfully refuted. R1b is no older than 18kya and origins are southwestern Asia. R1b was most likely not in Iberia before the Younger Dryas and the idea that we will find R1b in the Upper Paleolithic is pretty much absurd. I think those in HG I have been experiencing difficulties to find some continuity that just doesn't exist from this time frame in Western Europe, or even elsewhere for that matter. So far, the late and early Neolithic is the best we get. Mesolithic finds have not yielded R1b anywhere in Western Europe. Not to say R1b couldn't have been in Western Europe at this time, I just don't think it emerged from this region prior to the Younger Dryas. I just have a hard time understanding why it would be so difficult for a band of R1b people to travel across the stretches of the vast Eurasian plains into Western Europe during the Mesolithic. That's like saying early settlers couldn't discover Alaska because they didn't have planes. I'm sure a few R1b people wandered into the far west of Europe, but doesn't necessarily mean their "ancestry" emerged there.
I’m sorry to bug you, but do you know of any Mesolithic
finds in Western Europe that have yielded any Y-DNA haplogroups?
Nul, nil, zilch, zero, nada.