Do not flash random open-source firmware (like OpenWrt) before unlocking the cellular modem. The modem chip (MDM9230) has its own lock. Flashing the router OS does unlock the 4G modem. You will simply break your Wi-Fi while the SIM is still locked.
If the SIM’s MCC/MNC is not on the list, the modem refuses to attach to the network and sends the "Invalid SIM" message to the router CPU. zte mf283u unlock
Technical steps (generalized)
Do not flash random open-source firmware (like OpenWrt) before unlocking the cellular modem. The modem chip (MDM9230) has its own lock. Flashing the router OS does unlock the 4G modem. You will simply break your Wi-Fi while the SIM is still locked.
If the SIM’s MCC/MNC is not on the list, the modem refuses to attach to the network and sends the "Invalid SIM" message to the router CPU.
Technical steps (generalized)