An answer from another question linked this article https://en.wikipedia.org/wiki/Guangzhou_Television_Cantonese_controversy which says:
Due to Mandarin’s status as the official language, use of the country’s other languages in television as well as radio and film is rigorously restricted by the State Administration of Radio, Film, and Television (SARFT).[6][7][8] Permission from national or local authorities is required for using a dialect as the primary programming language at radio and television stations.[7]
Is there a list of all approved languages for use by SARFT?