It’s somewhat confusing, but according to Monsters and Critics,
“Under the revised Language Development Bill, Taiwan will stop defining Mandarin Chinese, the lingua franca of China, as the ‘national language.’
Instead, it will list Mandarin Chinese, Taiwanese, Hakka and Taiwan’s aboriginal tongues as its national languages, Chiu Chuang-liang, director of the cabinet’s council for Cultural Planning and Development, said.
It seems that Mandarin Chinese is being demoted from _the_ national language to _a_ national language. While such a move doubtlessly has international political ramifications, it also means greater recognition of the local peoples.
The number of languages in Taiwan appears to be dependent on the person counting, with the article citing “about a dozen tribes”, Travel in Taiwan counting nine mountain tribes, and Taiwan Tribes counting 13. The latter, moreover, with its tribal breakdown and count of 21 languages, makes it clear that it is the ethnic complexity causing the disparity in numbers. Wikipedia counts 25 tribes with only 14 living languages. Ethnologue gives 22 living languages including three Chinese varieties, Japanese, and Taiwan Sign Language, plus four extinct languages.