Xiaomi 12t - TrebleDroid/treble_experimentations GitHub Wiki
Unlock the bootloader
#Flashing Procedure
fastboot reboot fastboot
fastboot --disable-verity --disable-verification flash vbmeta vbmeta.img
fastboot --disable-verification flash vbmeta_system vbmeta_system.img
fastboot erase system
fastboot delete-logical-partition product_a
fastboot delete-logical-partition product_b
fastboot flash system system.img
fastboot -w fastboot reboot
NOTE
(If for some reason formating through fastboot doesn't work then try formating data through recovery)
Tested AOSP 13.