No-wipe newflasher upgrade flow for the XQ-EC72, keeping Magisk root.
Includes the Linux procedure for re-enabling US 5G over the Qualcomm
diag port: the pyserial EFS2 client, the policyman band files that get
written, and a backup of the device's original band config.
Claude-Session: https://claude.ai/code/session_01Ctisr9uXe4H8XsscZ2exGE
