Yes, after a long day of triing, i made it work. And i'm on Android 12!if your unit exactly Att then this will work flawless, bootloop because you comeback from other version (you can solve bootloop by hard factory reset with button).
btw, bring download mode back and flash KDZ is bestest way to full recovery partitions of the phone.
but there is no kdz of Att version rightnow.
so only 1way to clean back to Att stock is follow that method with Qfil.
* NOTE: Be careful for keep your imei and modem partitions.