You talk about issues of immigration, but China has a system that maintains internal passports, where citizens need permission of the government to move, and should they do so unofficially they face serious discrimination, and a denial of basic services. [2]
None of this of course, discusses the labor camp system, the imprisionment of political activists, or the murder and organ harvesting of religious minorities.
Just because you may not have heard of an issue doesn't mean that they don't exist, particularly when dealing with a country whose Human Rights records is one of the worst in the world.
[1] https://www.theguardian.com/world/2018/jan/25/at-least-12000...
[2] https://www.economist.com/news/special-report/21600798-china...