For most people, paying $12-15 for a professional unlock service with guaranteed new firmware is the smartest path. For enthusiasts, manually flashing a generic B21 firmware via TFTP is a satisfying weekend project.
: This complex process often requires opening the router to "jump" terminals, putting it into boot mode, and using tools like the ZTE Download Tool to install new firmware. DC-Unlocker zte mf283u unlock firmware new