They have a new service (not sure if it’s in Italy yet), where you can get AppleCare at any time, not just within the first 60(?) days. The catch is that it’s designed for people who have multiple Apple products they want to protect. If you just have the iPhone, it wouldn’t make sense.
looking at the site I found it but it tells me that I don't have any suitable device, I have an iPhone 15 so I don't think it's the fault of the device but of the country
This is possible. I think devices outside of the normal range may need inspection to be added. If it would an inspection issue, I’d expect it would tell you that instead of saying it wasn’t eligible.