To know the rules in force with the various countries when you are travelling from/to Italy you can consult the following sources:
INTERNATIONAL VOYAGES: www.viaggiaresicuri.it is the website that the Italian Ministry of Foreign Affairs has prepared for the information of travelers
Update: 01/05/2022 Easing of travel rules. From May 1st it will be enough to have a certificate of vaccination, recovery or a negative test.
SARDINIA: from 23rd of May is no longer obbligation the Covid test
SICILY: for anyone arriving in Sicily there is no longer obbligation Covid test
TIRRENIA shipping company:
GRECIA: https://travel.gov.gr/ #/.
Starting from 1 May 2022, travelers are NO longer required to present the Covid-EU Digital Certification (so-called "Green Pass"), or equivalent for entry into the country.
ALBANIA: http://www.viaggiaresicuri.it/country/ALB
Starting from 1 May 2022, travelers are NO longer required to present the Covid-EU Digital Certification (so-called "Green Pass"), or equivalent for entry into the country.
MONTENEGRO: http://www.viaggiaresicuri.it/country/MNE
Starting from 1 May 2022, travelers are NO longer required to present the Covid-EU Digital Certification (so-called "Green Pass"), or equivalent for entry into the country.
CROAZIA: https://entercroatia.mup.hr/ http://www.viaggiaresicuri.it/country/HRV
Starting from 1 May 2022, travelers are NO longer required to present the Covid-EU Digital Certification (so-called "Green Pass"), or equivalent for entry into the country.