Dimallum, ancient southern Illyrian toponym, today Dimale, in Albanian:
Looks like we didn't learn this toponym from any foreigners, it's outside of Arber region and it's more south than Lezhe, Durres, etc, and below the Jiricek line.
The town of Ulqin doesn't seem to be learned from foreigners either, it's connected to the Proto-Alb word for wolf. Also outside of Arber region, more north west of the Jiricek line
The middle latin name for Ulqin was Ulcinium which plausibly would have become Ulqin in Albanian if it entered at this state. So this cannot necessarily be use to argue a pre-roman knowledge of this toponym in the proto-Albanian vocab.
The toponym Dimallum didn't survive into any modern Albanian toponyms though, so it was lost, and cannot be used to argue any continuity of proto-Albanian speakers in that region.
As for the etymology, I actually agree that it is most probably cognate with Albanian
Mal, but so is Dacian
Maluensis, so this doesn't mean it is a proto-Albanian toponym.
If you are going to argue Dimallum means Illyrian was Albanian, then you have to argue Dacia Maluensis means Dacian was Albanian.
Single cognates are not enough to establish descendance from a language, it is the phonological system which does that.
Also, the earliest recordings of Ulqin are Oulkinion and Olcinium. Proto-Albanian should have been just Ulkinium.
The Oulkinion has been just to argue that this is a case of Illyrian /l/ giving /ul/ ( remember, l, n, m, r in Illyrian gave ul, un, um, ur, unlike in Albanian) hence this variation with /ou/
Regardless, the toponym of Ulqin being related to wolf is just one
possible etymology, there is another that it is related to uelk- (wet), obviously referring to the sea.
As we get closer in the tree to pinpointing the proto-Albanians, we should expect to find more and more cognates that are shared, but we cannot stop and be satisfied with just finding related language,
but the exact dialect that gave proto-Albanian.