Jejueo (8409-jje) = Endangered (80 percent certain, based on the evidence available) (Jejueo is used primarily in informal settings (e.g., in the home), largely by elderly speakers with a strong sense of ethnolinguistic identity. Moreover, here is reason to believe that many people born and raised on Jeju Island speak a colloquial variety of Korean that is in fact a mixed language that draws mostly on Korean but includes some Jejueo as well.)
Glottolog
[jje] at ISO 639-3
[jje] at OLAC
[jje] at IMTVault
Jeju at Lexibank
Jejueo at Endangered Languages Project
Wikipedia
Wikidata