So, I'm coming back to this thread after traveling to Korea for a month in september. No one replied here but who knows, maybe someone has the same questions and worries I had.
Since I didn't know how to start preparing for the trip, I tried to search on the internet about travel experiences and tips but I couldn't find really helpful ones. The only one I can REALLY recommend is the korean restaurant card, this one is a lifesaver, especially if you can't speak korean. Other than that I found like one page that recommended a few restaurants/cafes/bakeries that were supposed to be glutenfree. Since the page were some years old, these tips were not really up to date but it was all I had. My friends are real angels, they knew about my condition and what I couldn't eat and so on and they were really considerate. They always were down to search for glutenfree cafes or restaurants. But let's get back to the topic. ^^
I was there for 5 weeks, so we were in a airbnb. If you're staying in a hotel or a guesthouse you can always ask wether they can provide something glutenfree for breakfast. Being there we realized, that it's cheaper to eat out and not cook at home( eventhough we sometimes cooked at home). Let's start with restaurants! When you're in Seoul you can find many different restaurants from traditional Korean to Japanese, Indian and many more. When you have the restaurant card with you, Iwould recommend to just look for a restaurant where you think the food looks good and ask them whether they have something glutenfree in their menu. My friends and me all have decent Korean skills, so we always asked in Korean, but reading it is always better than only hearing it ;) A restaurant franchise we ate at in different places and cities was 김밥천국. Eventhough the interior is always really awful it's really authentic and the food is cheap and good. The 김밥천국 at the Anguk Station near one of the palaces has the best Kimchijjigae I ate in Korea (and I ate a lot Kimchijjigae...). Korean BBQ is always a good option because often it is not marinated. If you want a bit of a change I can recommend Vatos in Itaewon. It's a Mexican restaurant that serves 100% maize tacos. Another wonderful place is sunnybread. It's a cafe and restaurant that serves vegan and glutenfree burgers, and they're one of te best burgers I have eaten my whole life!
Enough of restaurants, let's talk about the real pleasure in life in Korea. Cafes! I actually only found 2 Cafes that served glutenfree cakes. One is the Nature Republic Cafe in Myeongdong, but I can't say anything about this, because the cake (only brownie) was so expensive, that we didn't go there :/ So the other cafe was Sunnybread the one I mention before. As you see this place totally stole my heart. The moment you step into their branch in Itaewon you feel like you're in heaven. Everything they sell is glutenfree, so no holding back! <3 they always have cakes, muffins, bread( it's sweet just so you know!), and so on. My personal faves are the peanutbutter chocolate bar and the sunny bread! Eventhough the food is on the pricier side, you won't regret a single won you pay. Before I saw a post that said that Cafe Thanks has glutenfree cakes, but it turned out that they don't sell them anymore. Cafes I recommend that don't have anything gutenfree but are a must-see for me, are the cat cafe and the ariate, both situated in Hongdae. Ariate is the most beautiful Cafe i've seen. It's filled with flowers the drinks are beautifully arranged(everyone gets a little flower). I think the cat cafe is self-explanatory.
We're almost finished. The only thing left are the bakeries. The only bakery I could find was Zero Bakery. They have two branches both in Itaewon. Their food is both gluten and sugar free. My friend and me went to both branches but we both liked the 경리단길점 branch better. It looks super adorable and it has a little place for sitting. The prices are okayish, I would say...My faves are the cheesetart, choco tart and the brownie(pure chocolate- I love it)!
Wow we're almost there.. my last tips is even if it sounds dumb- talk to people! The waiters and waitresses are always really kind and try to help. Of course sometimes there are rude people, but that's everywhere in the world the case. If you try to communicate, it will work out. That's what I learned. The waiters and waitresses mostly communicated with us in a mix of Korean, English and hands ("이거 NO!" *makes an X with his arms* when the waiter wanted to say that I couldn't eat the meal I asked about). They were always really friendly and understanding.
Since that sounds like a nice last sentence I'm gonna leave it at that, and I hope I could help someone out. If there's any question, that I didn't answer feel free to wirte me a pm or ask here.. but I'll probably answer faster if you're writing me directly :)