Love Casting OST 戀愛Casting

Hi, I haven't watched this show yet, but I subscribe to Yi Gao's Youtube channel, and I heard a really nice OST in one of his videos: https://www.youtube.com/watch?v=ybdrVxKX7m8

It starts around 1:30, and according to Yi Gao, it's a song from/for the series written/sang by some of the cast, and it doesn't seem to be any of the 3 songs you linked. Do you have any idea where it is, or if it's not, when it'll be released?