I visited South Korea on my U.K. passport. It was part of the greater trip which I created with the purpose of exploring ‘Two Koreas in One Go’. I was eligible for VOA. At the airport in Seoul, I had to go through this quarantine room, immigration room and finally customs room, as far as I remember. The health and safety issue is taken seriously inSouth Korea. I was asked health-related questions, like recent illnesses, surgeries, allergies, etc. I had a runny nose and got worried whether to mention it to the health inspector. I did. The man wearing a white mask was very reassuring and friendly, yet he still checked my nose.
More official info:
Foreign nationals entering Korea are required to have a valid passport and a Korean visa issued by the Korean embassy or consular offices in their country. However, citizens from many countries are now permitted visa-free entry for a limited period under certain conditions. In order to check whether you are allowed to enter Korea without visa issuance and for other requirements, please contact a Korean embassy or consular office in your country or visit the following websites to confirm.