I try not to make wild guesses.

And strong Urnfield Central European influence is well attested in Delmato-Pannonian areas, archaeologically
and genetically:
R-BY32273 Serb from Northeast Bosnia.
R-U152*, Serb, East Herzegovina, L2-, Z56-, Z192-, Y17161-, A7969-, S8024-. CTS5531, CTS4562, Y22447 still not done.
R-Y4354, Vlach Ugarak clan from East Herzegovina, Travunia, as well as Vlach Zotovic clan. Not related to Bulgarian R-BY184991, some distant R-Y4354 are also found in Greece, these might be Illyrian-Dorian connection. These really have no matches anywhere.
R-S14469 , Bosniak from Mostar, Herzegovina
R-L2>FGC13617 Montenegrin, Serb from East Serbia (admin),
Gheg ALB250fta, Kerkyra Greek
R-Y91536 , Montenegrin Brda tribe Moracani Bogicevci, from Hoti area by tradition, but per some documents one of them recently presented might be more likely from the Koplik area originally.
This is already some serious U152 diversity. They have no close ties to their cousins, usually way above 3000 ybp. I thought R-Y91536 is more likely Roman, but as you can see they are not related to anybody else and there is Slovenian R-Z37* with TMRCA of 3500 ybp so this fits better into Urnfield.
And Bosnia, Herzegovina, Montenegro are not some historically Celtic areas.
So 6 isolated U152 clades in the West-Balkans. More than enough to suggest these are descended of Urnfield movement. These might have linguistically formed the Delmato-Pannonian Illyrian complex. Whereas the "classical" Illyrian areas to the Southeast in Albania is where there is less U152 and much more J-L283, and these likely remained uninfluenced by the Urndield Illyrian wave. This is well attested in archaeology whereas in Pannonian complex the new Urnfield practice of cremation dominates in "classical" Illyrian areas the inhumation was dominant (J-L283 cultures all practiced inhumation).
There was that autosomally Northern Illyrian from Montenegro, but the coverage was bad, when I first saw him I thought he fits into these Central European newcomers who were likely "Celtic-like".