If you are a non EU citizen and wishes to stay longer than three months in Portugal, you will need to apply for a long-term visa or Portuguese residency visa. Those most commonly use this type of visa are workers (remote or relocated), Digital nomads, free lancers, retirees amongst others. The right Visa for those that checked this list is the Portuguese D7 Visa, which is valid for 120 days, this visa will also allow you to apply for a Portuguese residence permit after arrival. The D7 is the most common residency visa for U.S.A. citizens, Canada, New Zealand and Australia.
WHAT ARE THE BENEFITS OF A D7 VISA?
An alternative to the D7 is the Portuguese Golden Visa, Read about the Golden Visa here.