You may need an ETA for South Korea if you have a Portuguese passport

Visa-exempt travellers from select nationalities have the option to apply for a South Korean Electronic Travel Authorization (K-ETA) until December 31, 2024. Although not mandatory, travellers who acquire a K-ETA are not required to submit an arrival card at the port of entry. Beginning January 1, 2025, travellers are required to apply for an Electronic Travel Authorization (K-ETA) before travel. Travellers can apply for and purchase a K-ETA entirely online. Once the application is approved, travellers receive their K-ETA confirmation electronically.