I think there is a [smear campaign against Adrian Zenz])https://www.wsj.com/articles/pro-beijing-online-campaign-targets-u-s-based-xinjiang-researcher-cybersecurity-firm-says-11659607252), more here.

https://www.rand.org/pubs/articles/2021/chinas-disappeared-uyghurs-what-satellite-images-reveal.html and https://www.theguardian.com/commentisfree/2020/sep/24/china-imprisoning-uighurs-satellite-images-xinjiang are other sources based on what can be learned from satellite imagery. There are also interviews with escapees, e.g. https://www.theatlantic.com/podcasts/archive/2021/08/uyghur-genocide-china-us-immigrant/619806/ https://www.aljazeera.com/features/2018/9/10/escape-from-xinjiang-muslim-uighurs-speak-of-china-persecution https://thewire.in/rights/china-uighurs-xinjiang-camps-human-rights.