On our trip to Sicily in October 2021, I decided to go with Wind Tre,
After spending 15-20 minutes at 2 different Wind Tre shops (I went to 2nd one because I thought I might have had inexperienced people as the 1st one), the staff could never set it up. I don't know if it was their system, or my US Passport which caused the problem.
Went to TIM and was set up in 2 minutes.
Coverage was great in Sicily, Milan and Venice.