Are there really computer-literate Mandarin speakers in China who don't know pinyin? How do they input text? The only serious non-pinyin IMEs I'm aware of are the bopomofo ones for traditional characters in Taiwan.

Mandarin speakers in some parts of China speak their Mandarin differently, so can't remember the exact pinyin. E.g. around Wuhan people can't remember whether a word ends with -ang or -an, similarly with -eng and -en. As a foreigner, I can't remember nu and nv, similarly lu and lv. Beijingers have trouble with -r endings.

I've regularly seen people use the handwriting IME in China. They were probably only post-PC computer literate, though :)

many older people like my dad, don't know pinyin well. he doesn't input texts, but he browses web sites. He uses a default home pages full of links to start exploring the web.