I mean, considering they inhabited northwestern Italy near the French border, who else could the Ligurians have been if they were not some sort of Greek substratum that magically explains the E3b high in he area. I really doubt it as their language and customs are distantly similar to Celtic and because of all the aforementioned evidence and due to their geographical position in Italy, I give to them a Gallic origin, and if not, I would at least say they are celts, that may have arrived in southeastern France from the Halstatt culture or la tene culture or more probably as they were called Ambrones, they have a north Germanic origin, which may be that "factor" that makes them Ligurian instead of Gallic Celtic as most surrounding tribes are....there's a small possibility they may be celtiberians tribe as well but I truest doubt this and would either ascribe them a Gallic , but more probably Germanic origin.