What languages have been approved by SARFT for use?
Personally, I don't think there is a list for this.

Local radio and TV stations are allowed to broadcast with dialect within Local ONLY.

For example, 广东卫视 is broadcasted in Mandarin and is available to every province in China. While, for example, 南方卫视 and 珠江频道 are broadcasted in Cantonese, which is ONLY available within Guangdong Province.

Generally speaking, Radio and TV station are in 2 categories, available to every province and available within a specific province. I believe every province has many stations for both type.

Also, dialect varies a lot even inside Guangdong Province. Taking "accent" into consideration, Cantonese in Guangzhou, Zhongshan, Maoming, Dongguan, Qingyuan sounds different. Not to mention Teochew dialect and Hakka Chinese, all inside Guangdong province. For Teochew dialect, the difference of Chaozhou and Shantou is more than notable.

That's why I believe, it might be not possible to list all approved languages.