Note 12S Flashing Guide for AOSP ROMs 4.19

MAKE SURE YOU DOWNGRADE TO MIUI 14 or HyperOS 1, before proceeding with install.

1. Flash boot.img:

fastboot flash boot boot.img

2. Reboot to recovery

fastboot reboot recovery

3. Format data / Do a factory reset

4. Sideload rom via SD Card or ADB sideload

adb sideload name_of_the_rom_pacage.zip

5. Flashing Gapps (optional)
After flashing you will be asked to reboot to recovery. Select YES.
Once rebooted, flash gapps package like you flashed ROM.

adb sideload name_of_gapps_package.zip

or select from SD Card.

6. Reboot to system by selecting in recovery.