Нет у тюркского «серебра» нормальной этимологии, это в общем-то известно.
Appearently one of the pillar stones of the paper omits a very substantial work. The 2011 study by Antonov & Jacques (“Turkic kümüš ‘silver’ and the lambdaism vs sigmatism debate”)
It argues that the Turkic etymon for ‘silver’ should be reconstructed with a final lateral (written there as *ɬ / *ɫ in older literature), not -š.
If Antonov & Jacques’ reconstruction is accepted, the Turkic form underlying modern gümüş / kümüš is compatible with an original lateral — that makes the Arin/Yeniseian form with final -š more plausibly a Turkic → Yeniseian borrowing, not the other way around.