MIUI is Xiaomi's Android skin and a long time ago, the company used to develop its UI for non-Xiaomi devices. These days, Xiaomi doesn't do that anymore, but it does allow its devices to be unlocked and flashed as the customer pleases. The company even offers full ROM files on its community site. MIUI 10, based on Android 9.0 Pie has been successfully ported to both the OnePlus 6 and OnePlus 6T - unofficially, of course. Given the nature of different Android skin frameworks, not everything will work from the get go. The post is based on Xiaomi's 8.11.23 build of Android Pie and in order...
Source: https://www.gsmarena.com/miui_10_ported_to_the_oneplus_6_and_6t-news-34696.php