Shake Shack is always a good bet for gf burgers, and there are several locations in Seoul. They spoke English here and had no problem with my request for a lettuce wrap. (I didn’t ask for a gf bun since I heard those are less common outside the US, so I’m not sure if this location offers them.) The burger was delicious and I didn’t get sick.
— Somewhat
— No gluten-free information on the menu
— Some
— Excellent