According to multiple news outlets in Korea, Delta is to launch Portland-Incheon nonstop, 3/w, A332, from September 2021. The schedule is not loaded yet, but ICN airport announced the news today. Haven't found an English article yet, but here's one Korean article:
https://news.naver.com/main/read.nhn...aid=0004622389
Announced schedule:
PDX-ICN 1235pm-505pm+1 Mo Th Sa
ICN-PDX 730pm-225pm Tu Fr Su
The schedule will be convenient for MNL connection.