Guess where J2b-L283 presence will be, exactly, the Western Steppe!
Also, knowingly from all of the many samples we have and are going to get, Proto-Illyrians were heavy J2b-L283. There is also no correlation between J2b-L283 and R-Z2103 whatsoever.
There might have been one in the beginning, like we find R-Z2103 beside J-L283 in Maros and we have R-Z2103 in the East Adriatic (Pre-/Cetina period). So its possible, I'm just saying possible, that there was an early connection - I wouldn't even exclude that for E-V13 too.
However, R-Z2103 is pretty old and diversified, we will find many dead end branches, while J-L283 and E-V13 experienced both unique founder effects from the EBA-MBA, which made them the top dogs in their respective sphere of influence.
Like R-Z2103 was present around Cotofeni, we know that the Cotofeni people, which were more local Carpathian, partially copied the Yamnaya kurgans, but gave them their own style and inventory so to say. But the two groups remained largely separated - gene flow hard to estimate but likely present.
For J-L283 we really have troubles to connect it early on, but what we know is that latest by the MBA, the Proto-Illyrian autosomal profile was already developed and expanded. Its therefore good for this video to let it start around 1.600 BC, which is when at the one hand Tumulus culture pushed them somewhat West and they were already moving with the whole package. Because what was before is, as of now, completely open.
We need Cetina samples for comparison, Apennine Italians, Castellieri - and it will be interesting to see in which exact group J-L283 was earlier, around the Carpathians, when coming in from the steppe presumably.