Oh, Grom is excellent. And for some reason Lisbon has no shortage of fantastic Torinese gelato here.
Equally good if not a touch better is
Nivà. They've won tre coni ratings (the top) from the Gambero Rosso in Italy, which has never steered me wrong. The Gambero Rosso even rated it the #1 gelato in Italy back in 2023. Dangerously, it's five minutes from my apartment.
https://www.gamberorosso.it/guide/gelaterie-ditalia/