The region of Dardania was inhabited by Celts, Thracians and Illyrians. there were Celtic tribes that assimilated and were later in time seen as illyrians) by historians.
According Myths and History we have
1) A possible devastasion of Celts Before Hommer at Kadmus times (1500-2000 BC) which create a retaliation movement of Ilyros and its Pelasgians That mix is considered the genesis of Illyrians,
as Son of Illyros is mentioned the Keltos (Celt) so we see a connection with Celts
1b) Bryges (Phrygians) are mentioned by some as celtic Brigandi but in ancient times their taxonomy was as Thracians or para-Thracians
2) Scordisci Serdi Galates (gauls)
In historical times Celts manage to penetrate Illyria even Greece and Delphi,
the term Scordisci is Celtic and means scattered it is probably an esonyme
Scordisci are mentioned to draw back at Nis Serbia parts of Kossovo and then pass Istros (Dunav)
as Scordisci origin are mentioned some Byzantine Emperrors like Ioustinianus
Scordisci are also considered to Build the white city (Belingrand)
we don't have linguistic evidence of Scordisci but we know that had society and inner construction like the La Tene ones
Serdi are mention to settled around Sofia Bulgaria
Galates after the repel of their entrance to Greece are mention to settled in ROmania first, then to Bulgaria in Scanza Mountains (today area of Haskovo till sea) and then moved to minor Asia next Pontic Mountains,
WE know that they Speak a language simmilar to Belgae
so as a conclusion in what ROmans say Illyricum there was Celtic activity,
Greeks mention Half Pannoni Basin as the land of Keltos,
in what we call Illyricum proprie Dicti (Illyria) we don't have historical data about Celtic
but we have myths that mention Celts (early or proto -Celts since we speak about 1500-2000) and Pelasgians are the fathers of Illyrians
The Historical data show a possible settlement of Scordisci to Kossovo areas since their center area was Naissus. as also that scordisci passed North of Dunav and even build the city upon which Belingrad is Built,
Scordisci at 2nd 3rd Century AD are considered to be fully Romanised and mainly serve Roman Legions especially the
IV Flavia,
THERE IS POSSIBILITY THAT SOME Latinophones, AROMANI (VLACH) POPULATION IN THE AROUND AREA TO BE FROM SCORDISCI ORIGIN