That kind of market share in volume is useless. The market share in value is much more relevant. Selling 100 usd smartphones is not the same as selling 1000 usd smartphones.
Apple 44%
Samsung 16%
BBK Electronics 16% (Oppo/OnePlus/Realme 8%, Vivo 8%)
Xiaomi 8%
Others 16%
That's according to Counterpoint Research [1]
Profitability appears to be even more skewed in favour of Apple but I don't know the exact numbers.
It would be interesting to know what's included in that 16% others category as that's where any challengers would be coming from.
[1] https://www.counterpointresearch.com/global-smartphone-reven...
https://web.archive.org/web/20160423202414/http://www.dg.gov...
Unfortunately, I don't know what the authoritative source for company information is in China. It can't be blog posts and media reports I suppose.