Yes, we host many many sites that have an .it domain. However, we do not support purchasing .it domains through Netlify. What page were you on when you saw that message? If you could provide a screenshot of that message showing the browser address bar as well that would be quite helpful.
As to actually using the domain on your site, a DNS zone for that domain exists under an account owned by someone named Pawel. We’ll need that DNS zone deleted from Pawel’s account before you can use it on yours. If you know this person, please ask them to delete it. If not, write us back and we can do this a different way. Thank you!