Always back up your IMEI and calibration data before flashing.
While "exclusive" firmware is often guarded in private forums (like 4PDA or specialized Telegram groups), there are three primary ways to upgrade: 1. The "Web UI" Method (Easiest)
Gain access to real-time RSRP, RSRQ, and SINR data that is often hidden in the standard UI. Identifying Your Current Firmware Version