Chinese against Uighurs?

China is fairly open that the camps do exist. We also have various credible government leaks describing the size of the operation.

It should be noted that China maintains these are re-education camps intended as an anti-terrorism measure. Given their history, this is likely to be correct. To the west, re-educating to erase ones culture can be considered a cultural genocide. But since it doesn't have the same effect as an ethnic genocide (eg mass killings) the reaction is a lot more muted.

What China does deny is that the people inside these camps are used for labour, e.g. what is effectively slavery. There's decent evidence to suggest this is the case, but the full nature of this is not really well-known afaik.

Ukrainian Banderites in the Donbas? Exercise for the reader

The only ones to ever claim that was Russia, and they never provided any credible evidence for it. It also conveniently came after some political developments in the rest of Ukraine didn't go Russia's way.

The west still has free media outlets (the US less so, but in Europe the situation is better at least). Investigative journalists would definitely have jumped on a story like that if it were true, but they never managed to prove any of it.