Yes, Greek has substrate words, but people who are not closely involved in the field must be cautious about this material. Wikipedia is, as always with historical-linguistics issues, well behind the state-of-the-art in the field. Also, the largest works on Pre-Greek were Robert S. P. Beekes’ 2014 monograph Pre-Greek and his 2008 etymological dictionary of Greek and it is easy for a layman to accept these claims. However, Beekes’ work has been savagely reviewed; sadly, he was succumbing to dementia in these years and this affected his work. Subsequent scholarship, for example, has highlighted the fact that many of Beekes’ non-Indo-European words in Greek are not limited to Greek after all, and were presumably borrowed into an Indo-European dialect farther north.
Nice! Any sources on that?
With the success story of paleo-genetics we now know that any non-Indo-European substrates likely stem from the first wave of settlers called Early European Farmers who came via Anatolia and are directly related to the people who built Gobekli Tepe!