Didn't want to go too much off topic on the other thread, so I'm posting this here.
I've been looking into this Lubljana Culture too, and potential link to J-L283. It does seem like J-L283 may have come from further north in the Balkans during EBA, as suggested by J-YP91*, J-Z585*, J-Z615* samples. Interestingly, I think I read somewhere suggesting that those EBA Montenegro tumuli (Mala/Velika Gruda, etc) were part of Lubljana Culture expansion people..
Indeed. Govedarica wrote about some archaic links of Posušje culture with Ljubljana but he couldn't give some explanation. There is also issue of Litzen ware, common in Posušje. Per some views its point of origin are Eastern Alps. Also Ljubljana formed in few phases: Ig I, and Ig II, and apparently in Ig III Litzen ware appears. Ig I involved Vučedol, Ig II, Bell Beaker.
Slovenian Stane Gabrovec
In the EBA this whole area (Eastern Alps) is dominated by the Ljubljana culture, in the final stage with its Litzenian phase.
Some have tried to make Litzen = Ljubljana but Govedarica said Litzen came little bit later. Overall there seems to be some connection.
Part of Ljubljana was so called Middle Adriatic Ljubljana culture, some said crucial part of Cetina (on the other hand Cetina had clearly stronger Eastern influences much stronger than most of Yugoslav writers were willing to admit).
Actually reading about this Adriatic Ljubljana some of its elements also seem Adriatic EEF, living in caves.. Apparently there is no info on funerary ritual. So Govedarica says probably some EEF Mediterranean tradition.. Adriatic Ljubljana made plenty of influence on proto-Cetina in pottery..
So looking at it could be some IE J-L283, R-L51's who mixed up with E-L618 (might have been dominated by EEF's here).. These Eastern IE influences found in proto-Cetina are lacking. So yes it seems Cetina might have been formed by some Eastern IE influence.
Their site is Varvara A which had some Nakovana (late EEF) elements and ofc Varvara is a major Posušje (J-L283) center.. So it kinda looks to me this Ljubljana IE element might have been easily the J-L283. It's hard to pinpoint exactly but some of these details do point in that direction.
So Posušje culture was younger Varvara A3 and Varvara B1 (this is Reinecke chronology) and Adriatic Ljubljana was Varvara A1.. Search for "Gradina Varvara"..
Hmm I'm thinking Adriatic Ljubljana could be some non Posušje J-L283 lienage..
I didn't know much on Ljubljana and indeed Mala Gruda is Ljubljana, not Cetina and it seems non "Adriatic Ljubljana" either that is younger Ljubljana, Mala Gruda had a tumulus. As BB and even Slovenian Ljubljana had no tumulii I think this practice came from the East. No cremations (that was Cetina trait). And Posušje took the tumulii burial too so that might be another indication of a link.
Overall I'd say there are various indications that J-L283 indeed might be linked originally to Ljubljana culture. I'm thinking J-L283 = Ljubljana and these could have morphed into Posušje later or part of them at least.