On March 1, 2021 KST many K-Pop songs were disabled from Spotify.
Tablo of Epik High said “Apparently a disagreement between our distributor Kakao M & Spotify has made our new album Epik High Is Here unavailable globally against our will.”
Spotify entered the South Korean market on February, 2021 and Kakao M owns Melon, who is a direct competitor of Spotify.
Many K-Pop Groups and Soloists, as well as many K-Hip Hop acts have their music distributed by Kakao M, so until the dispute between them and Spotify is solved, some or the whole discography of the following performers is disabled.
You can also check the K-Pop Distribution Channels Table: 1thek, Stone, Bugs, Genie and others article to see which distribution company each group has.
Data source is this twitter thread. KHH means Korean Hip-Hop artist, some performers like Zico can be in more than one category.