Underrated less touristy destinations

I (23F) am heading to italy from croatia and have about 5 days to kill before i have to be in Milan and unsure where to go (also have about 5 days after Milan as well to go to Bologna)

i have been to the major cities, milan, rome, venice, naples so not super keen on going again but i am looking for somewhere nice n social for solo traveller. i love to enjoy the nightlife as well though im not expecting clubs etc just nice vibes drinking and meeting people

Anyone hv any recommendations of where to go?

been researching either cinque terre & amalfi coast, but also keen on Sardinia/Sicilly