I have serius battery draning in standby mode in the last MIUI 12 Version 12.0.1.0 ,First i did one normal update then i tryed to do all the flashes but whith the same result!
Unfortunately it's known that miui12 has a big battery usage. The only thing you can do is to root and flash custom kernel and GMS doze magisk module. I use NGK kernel with 10.xx touch driver and 1.7.7 GMS module. You can find it on xda.
