In your browser’s address bar, type (change IP to match your router):
A locked ZTE F670L means you cannot use it with a different fiber ISP’s network, nor can you change certain advanced settings. If you have canceled your contract, moved to a new provider, or simply want full administrative control, you need to unlock the device.
Immediately after unlocking, disconnect the fiber cable and disable TR-069 . That single server is what “re-locks” your router every night. Cut its access, and your ZTE F670L is yours forever.
A: Possibly, but with difficulty. Those providers use proprietary ONT authentication (like Verizon’s VZ SN). You would likely need to flash specific custom firmware.