Don’t miss Ciya Sofrasi in Kadikoy (take the ferry to the Asian side, fun). The best food I had all trip, by far (worth a long trip back the day of my departure for plane food ).
He has a few specialized restaurants in the same area now, but the original has interesting regional variety.
I also enjoyed the stuffed mussels sold by small vendors by the water, and the fried fish sandwiches in newspaper. I’d otherwise be more wary of streetside seafood, but they were popular with locals - and I was just fine
Oh also lahmacun and pide as a quick and inexpensive meal, with ayran to accompany.
My only disappointment was kababs - the most-recommenced place fell flat for me, which I attributed to expectations (they were under-flavored for me, which may have been regional).