These might be out of date (especially covid related) or touristy but places I enjoyed eating in my two short visits to Portland:
Nong’s Khao Man Gai - Probably the most famous cheap place. Hainanese Chicken, I’ve never been to Singapore to compare, but it was far better than the other US version I’ve had.
Eem - almost parodically hipsterish but it was fairly tasty thai-inspired food
Apizza Scholls - Good pizza.
Ox - Good Argentinian ~steakhouse.
Gumba - A pasta hole-in-the-wall which is again just absurdly hipster cliché but tasty and pretty cheap
Also not a big donuts guy but Blue Star Donuts was tasty. My wife’s uncle who lives in Portland treated it as some local treasure.
We stayed in an air bnb around Alberta Street and it was a fun area to stroll around. Cool city overall.