If you are looking for information about travel rules and COVID-19 requirements per country of origin, these are two essential sources of information in Portugal:

Website of the Portuguese Tourism Office:

https://www.visitportugal.com/en/content/covid-19-measures-implemented-portugal

Website of the Portuguese Borders Police:

https://imigrante.sef.pt/en/covid-19/faqs/#1596230859073-a1cdfe6a-4ada