@pparent
after a week of testing, the battery usage looks normal.

@MrT10001 said in Can NOT install UT Redmi note 9 pro "exit code 256":

Try installer version 0.10.0. Windows sometimes has an issue with fastbootd (which is not regular fastboot).

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!!!!!!!????!!!
W.T.Flag

I installed UBport Installer in my dev rig/linux and IT WORKED!!!!!!!!!!!!

$*&% windows

After about 20 hours, maybe more, of trying, it just came to: "just don't use windows dude"

The windows installer do not recognize the phone when it is in fastbootd mode, so it stops the process.

Thanks guys @MrT10001 @Vlad-Nirky for the help and support
Alex