I suppose it depends which "approved devices" list you're using. If I look at the US Department of Defense's approved products list I see Korean brands like LG and Samsung but I don't see Lenovo or Xiaomi:
"Chinese PC maker Lenovo has reportedly been banned from supplying equipment for the "secret" and “top secret” networks of many intelligence agencies, due to concerns its products are vulnerable to being hacked." ... "The ban is only thought to apply to the most highly restricted networks, and Lenovo remains a significant supplier of computers for “unclassified” government networks in these countries."
https://www.telegraph.co.uk/technology/news/10208578/Spy-age...
(That said, I have a Lenovo X1 Thinkpad, bought partly because of all the recommendations on HN, and in particular seeing Troy Hunt using Lenovo. I'd forgotten that article when I bought it.)