"Surface Mount Technology Portable" in this context refers to a hardware dongle or box (often branded as SMT Box or SMT Portable) that interfaces with a device’s motherboard directly via test points, UART, or EDL (Emergency Download Mode). Unlike simple USB debugging methods, SMT Portable bypasses software locks by communicating with the device before the full OS boots.
Tools like the Unlock your ZTE phone app provide unique unlock codes based on your device's IMEI number. unlock zte kernel zdroid smt portable