Device name : Mi MIX FOLD
Codename : cetus
Speed up tips : All methods have been fixed, the end.
Bootloader : You need to unlock the bootloader if you want to flash a rom into your phone via fastboot method, and your data could be deleted as you choose, please make sure you have backed up your personal data.Apply for Bootloader Unlock here.
MIUI Rom : Yes , go to the MIUI site: Mi MIX FOLD(cetus) - MIUI Official ROMs