It's now  uncontrolled airspace and therefore classified as ‘G’.

Not according to AIP Italy. What's your source?

Ok, so what you're saying is that it exists and is class D, but is only activated by NOTAM. I will pass this along to see if we can change its activity status in SkyDemon. Thank you.

Yes, said informally, in recent years they have never activated it, although it remains drawn on the maps.
It is the same Milano FIC that reminds pilots to consider it as G-space (the doubt comes to light among pilots, especially foreigners).

Thanks!