Tangping means 'lying flat'. It became a slogan around 2021 for young people who choose to do the minimum, rather than join the long-hours race for jobs, housing and status. Supporters see it as a quiet protest and critics as giving up. Dramas use it as a short way to place a character. Song of Life starts with a recent graduate who has been lying flat.
Where it comes up

Neon & Nine-to-Five
Song of Life: The Bilibili Original Where a Jobless Graduate Becomes a Funeral Makeup Artist
A guide to the 13-episode Bilibili original Song of Life: a jobless graduate who ends up as a funeral-home makeup artist, a trade Chinese television rarely shows, Zhou Yiran's lead performance, and why a well-rated show stayed little seen.