same for me mi 9 lite
what i tried to do:
booted to twrp 3.5.0.0 from fastboot: fastboot boot twrp.img
in twrp i saw strangy log: enablefilecrypto_failed
flashed Magisk-uninstaller-20210117.zip, rebooted but again fastboot loop
then i tried to extract boot.img from xieomi.eu rom and flashed...