The GMP international terminal was renovated about 10 years ago and has a few restaurants, both in the concourse and landside. IIRC the "best" one is before security/immigration, upstairs on 4F.

I'm a hard GMP fan since 90% of my travel is to Tokyo lol

Yeah, GMP these days has way more flights than before. Overall traffic will always be somewhat limited though, since that was part of the why they built ICN.

The other nice thing is if you want to take a taxi, the distance is so much shorter resulting in much more reasonable fares.

GMP also has the same Sky Hub lounge as ICN that I go to for a quick bite before long flights, and if I recall it has massage chairs 😂.

Would you expect a long immigration queue arriving after 10pm at GMP?
I am trying to figure out my transportation options.

Thanks

Gimpo in general has shorter immigration lines since there isn't as much international traffic. I've never seen long lines there and since you're close to the center of the city, transportation will be easy. I'd just take a taxi.

We went thought GMP 2 weeks ago, arrived around 9:20pm from SHA on OZ. Immigration was swift and k.ride pick up was right outside the terminal.

Thank you.
I was thinking of just taking a taxi too and not having to deal with public transportation.

FWIW, GMP is on the AREX airport express line and according to the official website, the last train headed into Seoul departs the Gimpo Airport Station at 12:22am (twenty two minutes after midnight).