for anyone who bricked his Xiaomi Mi 9 lite, like me yesterday. I tried several fixes, and today I tried downloading the Image file directly from Xiaomi (mi com).
I use a german / European / Global Version of the phone and it worked after installing:
miui_PYXISGlobal_V220.127.116.11.QFCMIXM_fde3fd51d2_10.0 with TWRP
I accidently installed yesterday already the V12 of Miui. So trying downgrading was failing on me. If you have the same problem, try just reinstalling V12 of Miui.
but I am just a noob, please only try if hope is already lost. Like it was on my side.