Is Portugal open for travelers from Turkey

According to IATA, the following foreign citizens may enter Portugal:

• nationals of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland (Rep.), Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Romania, Slovakia, Slovenia, Spain, Sweden and Switzerland, and their family members;

• passengers with a long term visa issued by Portugal;

• passengers arriving from Albania, Armenia, Australia, Austria, Azerbaijan, Belgium, Bosnia and Herzegovina, Brunei Darussalam, Bulgaria, Canada, China (People's Rep.), Chinese Taipei, Croatia, Cyprus, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Hong Kong (SAR China), Hungary, Iceland, Ireland (Rep.), Israel, Italy, Japan, Jordan, Korea (Rep.), Kosovo (Rep.), Latvia, Lebanon, Liechtenstein, Lithuania, Luxembourg, Macao (SAR China), Malta, Moldova (Rep.), Montenegro, Netherlands, New Zealand, North Macedonia (Rep.), Norway, Poland, Qatar, Romania, Rwanda, Saudi Arabia, Serbia, Singapore, Slovakia, Slovenia, Spain, Sweden, Switzerland, Thailand or USA;

So passengers traveling from Turkey or on Turkish passports are not included by default. However there's a "loophole" where you can first enter Croatia and then fly to your EU country of choosing. The IATA page has the following requirements for Croatia:

• passengers traveling as tourists with proof of paid accommodation;

The Croatian National Tourist Board confirms this:

Third-country nationals not covered by the above mentioned points may enter the Republic of Croatia from third countries if they are:

• persons who travel for tourist reasons and have confirmation of paid accommodation in a hotel, camp, private renter or rented vessel and other form of tourist accommodation or are owners of houses or vessels in the Republic of Croatia;

Persons referred to in items 7, 8, and 9 will be allowed to enter the Republic of Croatia with:

• Presentation of a certificate of negative PCR or rapid antigen test for SARS-CoV-2 listed on the Joint List of Rapid Antigen Tests Mutually Recognized by the Member States of the European Union, published by the European Commission, if the test result is not older than 48 hours testing until arrival at the border crossing.

So what you could do is fly from Turkey to Croatia (Turkish Airlines has non-stop flights to Dubrovnik and Zagreb), stay there for a day and then fly to Portugal. Note that you'll need a COVID test in both Turkey and Croatia. On the way back you could just fly straight from Portugal to Istanbul.