I take it back. It looks like holofly doesn't require registration.
https://esim.holafly.com/esim-italy/
https://esim.holafly.com/esim-italy/
To this thread - while my wife's TMobile connect phone worked fine without a higher data rate plan, it was not sufficient for navigation using Waze or Google Maps. It also did not work well for web browsing. She is insisting on spending the $50 for 30 days next trip.
My $50 plan started when it was supposed to and terminated when it was supposed to. it work quite well - not as consistent as my US TMobile coverage or speed, but sufficient for web browsing and for navigation.