> Pinyin Chinese is an international standard

A national standard, at best (in the PRC). In Taiwan, Zhuyin (Bopomofo) is universal, taught in schools and found on laptop keyboards, and romanisations are mostly following Wade-Giles rules. In Hongkong, Eitel romanisation is used even though their new commie overlords are forcing pinyin and yale canto down their kids' throats.

ISO and United Nations adoption don't qualify Pinyin as an international standard?

Using Taiwan as an example isn't really relevant given that it's majority Cantonese speaking, and Cantonese is a completely different spoken language than Mandarin.

Edit: I'm a clown. I was confusing traditional Chinese with Cantonese. Not the same thing.

Hong Kong is majority Cantonese speaking. Taiwan is not, it's Mandarin (and to a lesser extent Hokkien and Hakka but most young people prefer to speak Mandarin).

You're right, edited my original comment to correct. Thanks.

Are you sure Taiwan is mostly cantonese?

You're right it's not. I was confusing it with traditional vs simplified Chinese. Thanks for the correction.

Besides Pinyin, there is Cangjie, Q9, Dayi, etc. Plenty of other input methods are well in use. Though Pinyin is most widespread due to it being the way most kids are taught Mandarine.

There's lots of alternatives to Pinyin, some based on the Latin alphabet, others not like Bopomofo.

Not to mention any of the shape based methods like congkit