Our eSIM runs on TIM, Wind and Iliad, all three on 5G. Having three national networks on one profile matters more in Italy than in most countries, because coverage varies sharply between the north and the south.
5G is live across Rome, Milan, Florence, Venice, Naples, Turin and Bologna. 4G covers the rest, including Sicily and Sardinia.
The real gaps are in the Apennines, parts of Calabria and Basilicata, and the higher Dolomite valleys. Those are mountain problems rather than Italian ones.