Epirotans were Greeks or Illyrians ?

For Example the Pella curse tablet that signifies the greek dicalect spoken by macedons and epirots

The tab has been dated by the original publishers to the "Mid-4th century BC or slightly earlier (letter forms, spelling)". Prof. Edmonds of Bryn Mawr College prefers a 3rd century BC date.

The former opinion is supported by the Oxford Classical Dictionary, in which Olivier Masson writes: "Yet in contrast with earlier views which made of it {i.e. Macedonian} an Aeolic dialect (O.Hoffmann compared Thessalian) we must by now think of a link with North-West Greek (Locrian, Aetolian, Phocidian, Epirote). This view is supported by the recent discovery at Pella of a curse tablet (4th cent. BC) which may well be the first 'Macedonian' text attested (provisional publication by E.Voutyras; cf. the Bulletin Epigraphique in Rev. Et. Grec. 1994, no.413); the text includes an adverb "opoka" which is not Thessalian." (OCD, 1996, pp 905, 906).

Of the same opinion is James L. O'Neil's (of the University of Sydney) presentation at the 2005 Conference of the Australasian Society for Classical Studies, entitled "Doric Forms in Macedonian Inscriptions" (abstract): "A fourth‐century BC curse tablet from Pella shows word forms which are clearly Doric, but a different form of Doric from any of the west Greek dialects of areas adjoining Macedon. Three other, very brief, fourth century inscriptions are also indubitably Doric. These show that a Doric dialect was spoken in Macedon, as we would expect from the West Greek forms of Greek names found in Macedon. And yet later Macedonian inscriptions are in Koine avoiding both Doric forms and the Macedonian voicing of consonants. The native Macedonian dialect had become unsuitable for written documents."